In singleplayer world, and 'Illegal stance', click back to title screen botton,then go to multiplayer title menu

MC-231339 I tried to join my friend's multiplayer server, but it says, "incompatible Client. Please use 1.17." I'm glad they say please, but I am using 1.17 Resolved MC-10979 Hardcore Single Player Has Repeating Screens and Weird Links Resolved