Online checkin for Jetstar having booked through Qantas - not possible?

[Warks]

I booked a couple of reward seats on SYD-AKL with Jetstar (returning with QF) some months ago. Of course I used the Qantas website to do this using points. Yesterday when it came time to check in online I went to QF who directed me to Jetstar. I went through the various steps with Jetstar adding passport info etc until I reached the next step and it said there was something wrong and they couldn't do it, try again later etc. I tried the chatbot which posed the question whether I'd booked with another airline or agent. I said no in the misconception they were the same company. Finally I got onto a human chatbot who said I couldn't be checked in as I had booked with Qantas. They kindly added the passport info though.

I went back to QF (note there are two different booking numbers, one for each airline) and QF said that I couldn't check-in until 24 hours before my flight. Great! So I tried again this morning and it says to use the Jetstar code and check-in on their website! Catch-22 Airlines! Of course we can always check in at the airport but this is an unnecessary pain the bum process. I haven't flown Jetstar in about a decade but it was the timing of the flight that worked for me.
So unless someone else knows a way around this I'm checking in at the airport tomorrow.

Sorry to bother you, just a community service announcement in case someone has the same issue and is googling solutions in the future.