Happened to me for a few weeks. Then just started working out of nowhere. I believe alphabet agencies are targeting Tor nodes behind the scenes. Then I saw a few public articles supporting this idea. I think they are about to try and make Tor difficult to use to the point it will be hard to impossible

Get a webtunnel bridge from the tor website and add it as a custom bridge.

Working just fine on my phone 🤷

I have found that it often takes a very long time for Tor to build a circuit (bootstrap) using obfs4, because of what seems to be difficulty finding bridges.