You may have a corrupted install. Delete Facebook, restart your phone, then re-download via Purchased history.
If you have previously downloaded Facebook with your Apple ID, the App Store may allow you to download an older, compatible version. on your iPhone 6. Tap your Profile icon (top right) and select Purchased . Search for "Facebook" in the list of your apps. facebook for iphone 6 ios 12.5.6 download
and follow the steps in Method 1 above. The app will now appear in your "Purchased" history and offer the legacy version. 3. Use the Facebook Web Version (Recommended) You may have a corrupted install
Follow these steps to get Facebook on your iPhone 6 running iOS 12.5.6: on your iPhone 6
Your iPhone 6 will now proceed to download the legacy version of Facebook that is compatible with iOS 12.5.6.