Recently while working with datapacks, I attempted to use the /title command in its most simple version [/title title "Text"], I received the message in game saying: "Showing new title for UltraIsPending" but no title was displayed.

I brought someone else onto the server, running Java 1.17.1 on a Aseus Laptop and the titles functioned perfectly with them under the same conditions on the same server.

I was using optifine at the time but after trying it on vanilla it still didn't show.

These screenshots were taken immediately after each other, as you can see no title is visible