Facebook Error "Unable to log in. An unexpected error occurred. Please try logging in again." iPhone Android

If you’ve just unboxed your new iPhone 16, iPad, Samsung phones and are facing issues logging into the Facebook or Messenger app, you’re not alone. Many users are experiencing the error message:
“Unable to log in. An unexpected error occurred. Please try logging in again.”

"Unable to log in. An unexpected error occurred. Please try logging in again." 2025

This issue seems to affect not only the new iPhone 16 but also various other devices including Android phones and older iPhones. The problem persists even when users are able to log into Facebook successfully from a browser or another device.

In this post, we’ll break down why this is happening and what you can do to fix it.

What’s Causing the “Unexpected Error” on Facebook App?

This login error has become increasingly common, especially for users setting up Facebook on a new phone. Some of the reported symptoms include:

The Facebook app displays an “unexpected error” immediately after entering credentials.
Users can log in on Safari, Chrome, or their desktop but not in the app.
Messenger may or may not work depending on the device.
Password resets and app reinstalls do not fix the issue.
Some accounts seem to be partially blocked or caught in Facebook’s checkpoint system.

These symptoms suggest the issue is not related to incorrect login credentials, but possibly a bug in the Facebook app or a conflict during the login authentication process on new devices.

How to Fix “Unable to log in. An unexpected error occurred. Please try logging in again.” on iPhone and Android

1. Use Safari or Chrome to Log In First

Open Safari or your mobile browser
Go to: facebook.com/login/identify
Log in using your email/phone and password
Once logged in, scroll to the bottom of the page
Tap on “Open app”
This will open or prompt you to download the Facebook app
Because you’re already logged in via browser, the app will often bypass the login step

This method has worked for several users who had issues logging in through the app directly.

2. Delete and Reinstall Both Facebook and Messenger

Delete both the Facebook and Messenger apps
Reboot your iPhone
Open Safari and log in to your Facebook account
Use the browser login trick mentioned above to reinstall and reauthenticate the apps

This approach often clears any cached login data or token conflicts that are causing the error.

3. Log in via Messenger First

Delete the Facebook app completely
Download only the Messenger app
Log in via Messenger
After successfully logging into Messenger, install the Facebook app
Open a profile link within Messenger, which should redirect to Facebook and carry over login data

This method has helped many users bypass the unexpected login error.

Additional Tips

Make sure your Facebook app and iOS are updated to the latest version
Disable any VPN or firewall temporarily while trying to log in
Clear Safari or Chrome cache if using browser-based login methods
Try logging in using another Wi-Fi or mobile data network

Final Thoughts

If you’re facing the “Unable to log in – An unexpected error occurred” message on your new iPhone 16 or any other smartphone, don’t panic. This issue has been widely reported, and while Facebook has yet to offer an official fix, several user-tested workarounds are proving effective.

Logging in via browser first, using Messenger to initiate the authentication, and reinstalling the apps have all worked for many users. Until Facebook updates their app to fix this bug, these steps provide the best way to regain access.