Go into the file and attach a pdf. Exit. Re enter the file and delete the pdf. Check the diagnostics again.

Are you sure it says you have to attach? What are the words of the message?

Be sure to go to the PDF screen make sure nothing is checked off, if so un-check it; close client & restate Lacerte.   If you are still receiving the critical diagnostic error (CDE) and there are NO other CDR  that need to be addressed then you can override the CDE.    Go to EFile > Efile Support Tools > choose disable efile error.   Again be cautious with this tool as it will disable all efile errors even the ones you have yet to address.