If you try to link your Facebook or Instagram account on an Android device and receive:

“For your account security, logging in to Facebook from an embedded browser is disabled. To continue, download and log in to the Facebook app on your device and try again.”

You will need to allow external links in your Facebook app.

Fix the issue by opening your Android Facebook app, going to settings, tap on “Media”, and then enable “Links open externally”. You can then try linking your Facebook or Instagram account once more.

Unfortunately, there is currently no work-around for iOS devices.