I think it’s the same issue as this one (Juliaup appears to have corrupted julia language server information for vscode - #3 by brianguenter)
I tried updating julia to 1.12.6 ( I have 1.12.5) and it failed:
Checking for new Julia versions
Updating channel 1.12
Installing Julia 1.12.6+0.x64.w64.mingw32
Error: The system cannot find the file specified. (os error 2)