u/please_refresh

I have created dozens of these Powerpoints that look fine when I open them, and they look fine when I pdf them. But for some reason, the preview thumbnail versions all show text in white instead of black. First image is how it's supposed to look, second is how the preview image looks. I have no idea how to fix this! I'm not finding anything anywhere online to help me... One thought I had is that it might look different on a PC but I have no way of testing it. I just know the client will not be happy about this so I need to figure it out

Thanks you in advance!

Microsoft® PowerPoint for Mac Desktop Version 16.101.3 (25100321)