After completing the Class change option from barbarian to wizard all npcs, players, and items you can interact with no longer appears. Chat and UI functions are the only thing working.
I never had exactly this, my issue was for Jewelcrafter, ranking up gems, at one point I couldn’t rank gems anymore as that screen would “bug” my game into black screen with broken/corrupted looking like mistakes and unclickable buttons…
My solution had been to uninstall and reinstall manually the game, im pc.
I tried the “repair” but it didn’t do it, i really had to do the complete procedure, note that you will have to redownload updates and “data packs”(the rewarded cosmetic download files etc.)
I couldn’t keep playing like that for long for obvious reasons, I tried the repair button near the launch game button in bnet app, it didn’t fix,
I had to completely uninstall the game and then reinstall it for the fix to occur.