Fix Facebook Login Integration Issue

My existing “Log in with Facebook” flow has stopped working and users can no longer authenticate through their Facebook accounts. The button is already on the product and points to a registered Facebook App, but the hand-off to Facebook and return to my platform no longer completes successfully.

I need a developer who knows the Facebook Login SDK, OAuth 2.0, and the Facebook App dashboard well enough to:

• trace where the current flow breaks (front-end callback, redirect URI, app settings, or token exchange)
• apply the required code or configuration fixes
• confirm the solution in production and provide a brief summary of what was changed so I can keep it maintained

If you have recently resolved similar issues after Facebook API or policy updates, that experience will be very valuable here.