I raised the issue with support and @George_B said:
Facebook uses its own browser shell. He has to paste the link into the default device browser, Safari or Chrome for the app to function correctly.
Here are some posts on the subject. Facebook has a “mini” browser built in that does not support all browser functions, specifically PWA apps, which Glide is. As you can see there are ways to set facebook to open the system browser instead of the built in one.
Force open in Safari / Chrome from limited Facebook Browser - #2 by Jeff_Hager
I had an iOS user that experienced the issue that I described and I told him to open my app link in Safari directly. That solved his issue.