Some additional context: This is in react-native medplum sdk versions 3.0.2 (It was at 3..1.5 as an update BUT I thought maybe that was what was causing the error so I rolled back and still got it, this version matches current prod) When I inspect the response from oauth2/token I see a 200 response and I see id, access and refresh tokens along with my project name and profile name that I would expect. But SDK is throwing error that is being caught in a try...catch. I was trying to update to Expo SDK 51 from 50, this means I was bumping versions of Expo related packages. Going to play around a bit with downgrading some of those to determine if anything in there might be fighting with base64 encoding as it relates to medplum sdk

Attempted on both iOS and Android to verify wasn't singular platform.

I guess interesting note on the other existing project while I think about it is that it was started as a bare RN app adding in expo modules, this is doing the opposite. The original project is on Expo 50.

Sadly this did not solve the problem. I noted I had separate base-64 dependency I had installed in our original app before the expo-pollyfills were available and I was doign more manually login and otken exchanges. I attempted to see if it would make a difference if I installed that, unfortunately not. Running both expo-doctor and install --check have positive results without errors. Any other ideas?

Here's a snippet of dependencies

I made sure to eliminate all other calls surrounding it to verify. Obviously without it returning/grabbing the response properly then all other requests fail from there. I am going to spend a little time digging into the medplum code to see if I can finagle it at all. If I find anything I'll let you know