Whoops, missed this post. I posted a fix in Error code 34202 -- FIX -- version mismatch 1.0.2.41917 vs 1.0.2.42016 ; but tl;dr to avoid having to do a full reinstall:
- Open your Diablo 4 install folder (gear icon next to PLAY, select Show in Explorer)
- Select everything EXCEPT the folders. In particular, DO NOT SELECT THE DATA FOLDER (because that’s the 80gb content!).
- Delete what you selected. (Or if you want to be safe, move it elsewhere.)
- In battle.net, select “Scan and Repair”
- Wait a minute or two.
- Launch.