As with contacttower I did not receive any formal invite to sit the online assessments, I just logged into my recruitment account and looked in the assessments section and the links were there.
Thinking back through the fog of time to when I was not allowed to sit the online assessment I remeber that there was one link visible but when I clicked on the link and tried to start the assessment the window immediately closed and I had a message stating that I had completed all the required assessments.
That was when confusion got a hold of me and I emailed Jet2 recruitment for some advice.