CSS 3 validated theme.css throws Invalid CSS

I purchased the Bootstrap Phoenix theme v1.14.0 which is working fine in my app. Unfortunately when imported in Boostrap Studio, it throws Invalid CSS error. I used https://jigsaw.w3.org/css-validator/validator to validate it, erase the errors and got this response from the validator

Still when I import it throws Invalid CSS. Any ideas? There is still some warnings inside, but no errors.
Would appreciate help.

If possible can you send us the theme css so we can investigate further? You can send it as an attachment to bugs@bootstrapstudio.io