Usually with the paid offers I literally screenshot and time-stamp every page and step I do, then I send it all off in one go if there's a problem.

I had a problem with the Ladbrokes offer a while back that got sorted eventually.

It's always better to collect as much evidence as possible and send it off together than in bits, as the support ticket function is a little awkward when you're sending multiple tickets for the same problem.

Hope that helps

EDIT: and make sure you have any pop-up/ad blockers disabled, as sometimes these can restrict the trackers that the providers use to automatically award rewards.