Custom visuals - pdf export

Hello, we recently created custom visuals that we've made available in our organisational visuals section. The problem we have is that they do not appear when exporting published reports to pdf, is this  because visuals are required to be certified by Microsoft?

We only want these visuals to be internal and not made available externally, and I understand that certification means publishing them to the Appsource and removing them from Organisational visuals, which wouldn't work for us.

Any advice would be appreciated.