In Chat settings the Narrator button says "Narrator it not available" and you get the following error in the output log on startup:

• Windows

  [12:51:52] [Client thread/INFO]: [STDOUT]: ERROR : Couldn't load Narrator library : Unable to load library 'SAPIWrapper_x64': Native library (win32-x86-64/SAPIWrapper_x64.dll) not found in resource path ([file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/com/mojang/netty/1.6/netty-1.6.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/oshi-project/oshi-core/1.1/oshi-core-1.1.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/net/java/dev/jna/jna/4.2.2/jna-4.2.2.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/net/java/dev/jna/platform/3.4.0/platform-3.4.0.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/com/ibm/icu/icu4j-core-mojang/51.2/icu4j-core-mojang-51.2.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/net/sf/jopt-simple/jopt-simple/4.6/jopt-simple-4.6.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/com/paulscode/codecjorbis/20101023/codecjorbis-20101023.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/com/paulscode/codecwav/20101023/codecwav-20101023.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/com/paulscode/libraryjavasound/20101123/libraryjavasound-20101123.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/com/paulscode/librarylwjglopenal/20100824/librarylwjglopenal-20100824.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/com/paulscode/soundsystem/20120107/soundsystem-20120107.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/io/netty/netty-all/4.0.23.Final/netty-all-4.0.23.Final.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/com/google/guava/guava/17.0/guava-17.0.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/org/apache/commons/commons-lang3/3.3.2/commons-lang3-3.3.2.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/commons-io/commons-io/2.4/commons-io-2.4.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/commons-codec/commons-codec/1.9/commons-codec-1.9.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/net/java/jinput/jinput/2.0.5/jinput-2.0.5.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/net/java/jutils/jutils/1.0.0/jutils-1.0.0.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/com/google/code/gson/gson/2.2.4/gson-2.2.4.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/com/mojang/authlib/1.5.24/authlib-1.5.24.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/com/mojang/realms/1.10.8/realms-1.10.8.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/org/apache/commons/commons-compress/1.8.1/commons-compress-1.8.1.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/org/apache/httpcomponents/httpclient/4.3.3/httpclient-4.3.3.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/commons-logging/commons-logging/1.1.3/commons-logging-1.1.3.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/org/apache/httpcomponents/httpcore/4.3.2/httpcore-4.3.2.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/it/unimi/dsi/fastutil/7.0.12_mojang/fastutil-7.0.12_mojang.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/org/apache/logging/log4j/log4j-api/2.0-beta9/log4j-api-2.0-beta9.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/org/apache/logging/log4j/log4j-core/2.0-beta9/log4j-core-2.0-beta9.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/org/lwjgl/lwjgl/lwjgl/2.9.4-nightly-20150209/lwjgl-2.9.4-nightly-20150209.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/org/lwjgl/lwjgl/lwjgl_util/2.9.4-nightly-20150209/lwjgl_util-2.9.4-nightly-20150209.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/libraries/com/mojang/text2speech/1.5/text2speech-1.5.jar, file:/C:/Users/[USERNAME]/AppData/Roaming/.minecraft/versions/17w13a/17w13a.jar])
  

• Linux

  [STDOUT]: ERROR : Couldn't load Narrator library : Unable to load library 'fliteWrapper': Native library (linux-x86-64/libfliteWrapper.so) not found in resource path ([file:/home/[USERNAME]/.minecraft/libraries/com/mojang/patchy/1.0/patchy-1.0.jar, file:/home/[USERNAME]/.minecraft/libraries/oshi-project/oshi-core/1.1/oshi-core-1.1.jar, file:/home/[USERNAME]/.minecraft/libraries/net/java/dev/jna/jna/4.2.2/jna-4.2.2.jar, file:/home/[USERNAME]/.minecraft/libraries/net/java/dev/jna/platform/3.4.0/platform-3.4.0.jar, file:/home/[USERNAME]/.minecraft/libraries/com/ibm/icu/icu4j-core-mojang/51.2/icu4j-core-mojang-51.2.jar, file:/home/[USERNAME]/.minecraft/libraries/net/sf/jopt-simple/jopt-simple/5.0.3/jopt-simple-5.0.3.jar, file:/home/[USERNAME]/.minecraft/libraries/com/paulscode/codecjorbis/20101023/codecjorbis-20101023.jar, file:/home/[USERNAME]/.minecraft/libraries/com/paulscode/codecwav/20101023/codecwav-20101023.jar, file:/home/[USERNAME]/.minecraft/libraries/com/paulscode/libraryjavasound/20101123/libraryjavasound-20101123.jar, file:/home/[USERNAME]/.minecraft/libraries/com/paulscode/librarylwjglopenal/20100824/librarylwjglopenal-20100824.jar, file:/home/[USERNAME]/.minecraft/libraries/com/paulscode/soundsystem/20120107/soundsystem-20120107.jar, file:/home/[USERNAME]/.minecraft/libraries/io/netty/netty-all/4.1.9.Final/netty-all-4.1.9.Final.jar, file:/home/[USERNAME]/.minecraft/libraries/com/google/guava/guava/21.0/guava-21.0.jar, file:/home/[USERNAME]/.minecraft/libraries/org/apache/commons/commons-lang3/3.5/commons-lang3-3.5.jar, file:/home/[USERNAME]/.minecraft/libraries/commons-io/commons-io/2.5/commons-io-2.5.jar, file:/home/[USERNAME]/.minecraft/libraries/commons-codec/commons-codec/1.10/commons-codec-1.10.jar, file:/home/[USERNAME]/.minecraft/libraries/net/java/jinput/jinput/2.0.5/jinput-2.0.5.jar, file:/home/[USERNAME]/.minecraft/libraries/net/java/jutils/jutils/1.0.0/jutils-1.0.0.jar, file:/home/[USERNAME]/.minecraft/libraries/com/google/code/gson/gson/2.8.0/gson-2.8.0.jar, file:/home/[USERNAME]/.minecraft/libraries/com/mojang/authlib/1.5.25/authlib-1.5.25.jar, file:/home/[USERNAME]/.minecraft/libraries/com/mojang/realms/1.10.8/realms-1.10.8.jar, file:/home/[USERNAME]/.minecraft/libraries/org/apache/commons/commons-compress/1.8.1/commons-compress-1.8.1.jar, file:/home/[USERNAME]/.minecraft/libraries/org/apache/httpcomponents/httpclient/4.3.3/httpclient-4.3.3.jar, file:/home/[USERNAME]/.minecraft/libraries/commons-logging/commons-logging/1.1.3/commons-logging-1.1.3.jar, file:/home/[USERNAME]/.minecraft/libraries/org/apache/httpcomponents/httpcore/4.3.2/httpcore-4.3.2.jar, file:/home/[USERNAME]/.minecraft/libraries/it/unimi/dsi/fastutil/7.1.0/fastutil-7.1.0.jar, file:/home/[USERNAME]/.minecraft/libraries/org/apache/logging/log4j/log4j-api/2.8.1/log4j-api-2.8.1.jar, file:/home/[USERNAME]/.minecraft/libraries/org/apache/logging/log4j/log4j-core/2.8.1/log4j-core-2.8.1.jar, file:/home/[USERNAME]/.minecraft/libraries/org/lwjgl/lwjgl/lwjgl/2.9.4-nightly-20150209/lwjgl-2.9.4-nightly-20150209.jar, file:/home/[USERNAME]/.minecraft/libraries/org/lwjgl/lwjgl/lwjgl_util/2.9.4-nightly-20150209/lwjgl_util-2.9.4-nightly-20150209.jar, file:/home/[USERNAME]/.minecraft/libraries/com/mojang/text2speech/1.7/text2speech-1.7.jar, file:/home/[USERNAME]/.minecraft/versions/17w16b/17w16b.jar])

I'm not the only one experiencing this.