I don't know if this is a bug or a feature, but when I load a PowerPoint file in the preview pane the "current slide preview" becomes white. I would expect a preview of the current selected slide though just like the live pane behaves.
These are my Presentation settings in OpenLP.
Further information about my system:
Windows 10 22H2 64-Bit
Microsoft® PowerPoint® 2016 MSO (Versie 2211 Build 16.0.15831.20098) 32 bits
See Preview issues for presentations (#1278) · Issues · openlp / OpenLP · GitLab as well, the same issue is mentioned there.