Not sure if this is a good place for this post or not, but here goes.
I reject outbound connections to meta domains at the firewall. I noticed this banking app refuses to prompt for login credentials unless I am on mobile or a public WiFi network. I watched my FW logs and noticed many rejected connections to graph[.]facebook[.]com.
I contacted their support team, but they denied the connection was their app. I shared the screenshot on this post and they closed my case without comment.
I emailed the address on the Google play store and they also denied the connection was their app. I shared the screenshot and they asked if I downloaded the app from the play store, implying the official app doesn't do this, but of course it does.They closed my case without proper resolution as well.
Just thought I'd share this here so people know that some banks make direct connections to Facebook to share analytics, without your knowledge or informed consent, and they lie about it when called on it.
I don't think it's that connection causing problems, mainly because my app works fine (mostly) and I don't have a connection to any meta services. There are none on my phone, and I do not have a Facebook login at all. I will say that of all the apps I use, Ally is the most finicky. It seems to crash itself every 2-3 uses for no apparent reason at all.
That said, it seems unlikely that the app would fail for you in this case just because you blocked access to a service that I know it does not actually require to operate (because it has to be operating without it on my phone), and another poster tested and could not recreate. Not sure if that helps, but may point you towards diagnosing what is really causing the issue!