If you are seeing: All files Unknown% Statements 0/0Unknown% Branches 0/0Unknown% Functions 0/0Unknown% Lines 0/0 and an empty page for the output (im focusing on the .html output) then try this:
add the following text into your package.json under your scripts -> “coverage” or however you have your vitest coverage command set up.
"coverage": "vitest --coverage.enabled --coverage.provider=v8 --coverage.all"
this may fix your issue, hopefully. Change out v8 if using another provider.