@lokalu99 are you on v3.1.4 by now and did retest?
I brushed up my french and finally could register. I can confirm the failing login with proper credentials and created a logcat of the whole process that is… kindof intrusive.
duolingo wants to make sure there’s no Ad fraud, advertisers want humans see Ads, so it will run playintegrity checks. Imo - the log isn’t fully explicit (will attach) - its up to those that their abuse detection declines a login on my device (unlocked FP3). Different device (locked, no userdebug build) with better playintegrity verdict could maybe work.
In any case, AppLounge offers duolingo as PWA, or you can just use any browser to add it to the homescreen, less intrusive.
logcat
see pastebin for full log of process id (+microg), the relevant excerpt quoted here. The “ErrorResponse 401” is the unauthorized verdict by the login api
V DuoLog : [Growth - Reonboarding]: No credential found, skip
..
V DuoLog : [Growth - Reengagement]: Device Registration failed
..
I DuoLog : [Platform - Application Stability and Performance]: beginAsyncSection: abuse_req_cls_sig_measure
I PlayCore: UID: [10264] PID: [3503] StandardIntegrity : requestExpressIntegrityToken(4907901474386365734)
I PlayCore: UID: [10264] PID: [3503] StandardIntegrity : Initiate binding to the service.
I PlayCore: UID: [10264] PID: [3503] StandardIntegrity : ServiceConnectionImpl.onServiceConnected(ComponentInfo{com.android.vending/com.google.android.finsky.expressintegrityservice.ExpressIntegrityService})
I PlayCore: UID: [10264] PID: [3503] StandardIntegrity : linkToDeath
I DuoLog : [Data Platform - Experiments]: Track: {}
I PlayCore: UID: [10264] PID: [3503] OnRequestIntegrityTokenCallback : onRequestExpressIntegrityToken
I PlayCore: UID: [10264] PID: [3503] StandardIntegrity : Unbind from service.
I DuoLog : [Platform - Application Stability and Performance]: endAsyncSection: abuse_req_cls_sig_measure
I DuoLog : [Platform - Application Stability and Performance]: Tracking timer event abuse_req_cls_sig_measure with duration of 41 ms
I DuoLog : [Platform - Application Stability and Performance]: beginSection: api_call https://android-api-cf.duolingo.com/2017-06-30/login?fields=id
I DuoLog : [Data Platform - Experiments]: Track: {}
I DuoLog : [Platform - Application Stability and Performance]: endSection: api_call https://android-api-cf.duolingo.com/2017-06-30/login?fields=id
E Volley : [100] J.c: Unexpected response code 401 for https://android-api-cf.duolingo.com/2017-06-30/login?fields=id
V DuoLog : [Platform - Application Stability and Performance]: Network request error for /login: ErrorResponse 401 {}
I DuoLog : [Platform - Application Stability and Performance]: endAsyncSection: login_success_or_fail