CEP extension doesn't open or is blank

I have a CEP extension that works on my computer perfectly fine. It is available on Exchange so it passed the review/vetting process. Some of my customers however complain that they need to uninstall it and install again every time before they open Premiere Pro (the extension is a Premiere Pro panel).

Otherwise they cannot open the extension panel i.e. they see it in the Window -> Extensions menu but clicking on it does nothing. Or sometimes the panel opens but it's completely blank.

I cannot reproduce any of that on my computer so is there a reason why it might happen and how to go about debugging it (on a customer's computer)?

It happens on macOS and Premiere Pro 14.8 for sure.