This issue seems to mirror the one here MCPE-78342 except instead of a loading screen an error message along the lines of “sorry, something went wrong, please try again later or try on xbox.com” appears soon after. The accounts remain accessible elsewhere including the xbox site and app as well as microsoft websites. This issue seems to be exclusive to mobile users.
If your issue is similar to the one here: MCPE-78342 please comment, vote and follow the ticket, support team will prioritize bugs that affect the most users
Dirígete al ticket MCPE-78342 comenta, observa y sigue el reporte. Este usuario reporta el mismo problema, el equipo de soporte da prioridad a los reportes con más usuarios afectados. El ticket está en inglés que es el único idioma que esta página acepta.
There are multiple tickets about this issue already commonly reporting to be able to access the account on xbox.com and the xbox app as well as on microsoft websites. The log in page in the game seems to be the only place where the sign in can’t be completed. The recent reviews on the app store shows ios users having the same issue.
Running 1.16.0 on ios, can confirm xbox live sign in error has not been resolved. Updated behavior on MCPE-78342