1. If the client is locked, then unlock. Often that hampers the proforma

2. Are you sure you have proper data file path? When you do the proforma note where it will put the info, then go to 2019 to be sure your data path is correct

3. Are you using the 2018 program to do the proforma? The transfer is alway in the old program, not the new one. 

4. https://proconnect.intuit.com/community/schedule-k-1/help/reasons-a-client-file-will-not-proforma/00...

If none of these solve the problem, you may need to contact support.