It's not clear from your question what you're actually referring to.

Critical diagnostic is generated not for data import but e-filing rules checking.  In other words, you shouldn't get a critical diagnostic for importing a K-1 from 1120-S.

Import of K-1 works if the business return was prepared within ProConnect Tax.  Is that what you have?

https://proconnect.intuit.com/support/en-us/help-article/import-export-data-files/import-k-1-proconn...