This sounds like this issue: https://github.com/BetterThanTomorrow/calva/issues/1139 Do you, by chance, have the python extension installed? See here: https://github.com/BetterThanTomorrow/calva/issues/1139#issuecomment-832655477
If you do, and disabling it makes jack-in work again, then maybe we should look into what's going on there. If you don't have it installed, then if you can give us a reproducible project + vscode config, that would be helpful.