Invoice will not convert to PDF (windows 10)

Hi there, I am using the latest version 18.14.13.
But after d/l it today, I am unable to convert invoices to PDF. I receive this message … tried to put screen shot here but not working.

Please help. I have checked my PDF capabilioty on laptop and it is not affecting other programmes

  1. Are you using a custom theme? If so, switch to the Plain theme and try it.

  2. Did you change anything else when you installed the new version?

  3. Can you print directly using the Print button?