Deck support beam have come lose

[Dave22q]

I agree with those who see a simple non-structural cosmetic issue. Support beams break, they generally do not come loose. Also a 'deck support beam' would be supported from below not above If the dangling member does not bother you, leave the repair for a rain day. All you need to do is re glue it, bracing from below until the adhesive sets.

[Perna]

Agreed it looks like a deck support beam which isn't particularly close to the mast. This only became evident later on in your post.

It is not cosmetic in as much that you need it to support the deck but if you leave off having parties on the cabin roof for this season...

[Flod]

Latest update is that I tried to fix the problem. I have put a lot of sikaflex where the original glue was and also mounted two bolts through the deck. Now I will leave it for 12-24 hours and then hopefully the thing stays in place