you’ll likely need to create debug logs (logcat, logfox) to advance understanding of that issue. There exist one entry at microg, but it’s very thin. Also check microG settings as to what is enabled.
that a SMS is sent is good. I don’t think yet it is similar as only logs can tell, but here’s another case where SMS verification fails silently with no UI reason given. Ofc I’d be interested if it’s the same category of error.