I have a Nintendo switch, and I have a realms plus subscription.  Every time I try to upload a new world to the realm or try to play a new world on the realm it says "An error occurred" pretty much immediately (prior to even any uploading occurring; the connection is working fine; can play the world on the realm).  This has been for every world I try to upload for the past ~ 12 h (tried several).  I reset the realm and tried again, same issue.