Hi dop2000 , sorry for the late reply. As I've announced on the Discord Server, I'm away for a few months from game development because of school works. I will be back Mid-June or Post-June to fix, update and upgrade the plugin collection including the Mobile Facebook.
Reference : github.com/Scirra/Construct-3-bugs/issues/2457
What you are experiencing is the Facebook SDK conflict with the C3Runtime. As you've known, it works on C2Runtime. This happened, if I recall correctly, half a year ago. And I managed to patch it by filtering supported Facebook SDKs for the C3Runtime where a conflict wouldn't happen.
But only a month ago, we ran out of usable SDK versions, I forgot the last one, but once that depreciated, the Facebook SDK completely isn't usable with the C3Runtime anymore.
I want to deeply investigate the issue, but I would need to ask the Construct Team for support if it is in fact proven to be a conflict with the Facebook SDK and the C3Runtime. Which looks like it as per my initial tests.
I can focus on investigating this when I get done with all my work, thesis and internship which is by the end of June.