Not a bug, and frankly there might be a simple solution here.
So I got the new iPhone X, on the way to the airport. I’m currently in the UAE. My old phone is wiped.
How do I (current account preview) get access to the app? Do I download Testflight again and log in? I am now conscious that there are only a set number of places on there.
Also: I’m posting here as I don’t have access to the app, so can’t do the chat.
Yes. There are limited places and you have one of them allocated so there should be no problem.
Phew. It’s simple then. I’ve had a bit of a nightmare in general so far, so this is good news 
If you download TestFlight and log in with the same Apple ID you used before, you’ll be able to re-download the app 
Which is so much easier than First Direct:
When it comes to FD, their app security is a bit of a nightmare.
They wouldn’t let me add my FD debit card to ApplePay because I was in Sweden. WTF? Transactions going through my current account at the time showed I was in Sweden. I’d authenticated my personal details with them to their satisfaction. Purely because I was in Sweden they wouldn’t do it.
I tried through a VPN to show UK IP but still couldn’t add it.
It’s taken my wife years to actually work out how to log into her FD account …I think that prevents her from moving banks more than any cash incentive could entice her.
I had that yesterday. I haven’t got a new phone (living with trusty iPhone 6) but it still stuck me as a load of faff just to read let alone having to do it all.
My FD security key has been disabled for months due to wiping my iphone. I should ring one of these days to reset it…
Great though FD are, I really struggled to get my head around the Digital Key thing 
You and me both. It’s a right royal PITA.
I have just had new iPhone X downloaded the monzo app in TestFlight sets up then just keeps closing have deleted and downloaded three times now made contact in chat told will pass on to ca team but nothing can be done till Monday
The perils of early adoption,I guess. Good Luck.
Have you done the 11.1 update? May be worth updating then trying the download again.
Yes updated to 11.1 deleted app reinstalled works a few times then will not load
TestFlight version of CA app isn’t compatible with iPhone X unfortunately 
If you’re having this issue, DM me your email address that is tied to your account.
I have the iPhone X and it works fine!