Fresh install of v5 here, having problems with invoice PDF viewing and customisation in settings.
When trying to customise a PDF in settings I get a 500 error.
When trying to view the PDF of a created invoice, I get the login screen displaying on the PDF.
During setup the genterate PDF test was successful.
I’m having the same problem as @NoobKS92. I recently upgraded to 5.2.16 (via Softaculous), and on an installation that was working well before the upgrade, I now see the following when I try to view a pdf in Invoices: