Error 400 could be due to some temporary problems in the Facebook web site. Sometimes the error did not occur again after retrying sharing a trip later.
If the error 400 still occurs, try these steps:
1. De-authorize the BikeBrain app from a computer (not iPhone).
* use a computer to sign in the Facebook website.
* select menu at top right corner > Home > Account Settings.
* select left hand side menu > Apps.
* click the cross symbol at the right hand side of the BioLogic BikeBrain entry to de-authorize the app.
2. Then reset the setting from the BikeBrain app by doing this:
* press "More" in the lower right corner
* choose "Settings"
* choose "Sharing Settings"
* scroll down and find "Share Map via Facebook"
* choose "Sign Out"
* then choose "Sign In" again
* when prompted by Facebook, press the “Install” button and “Allow All” button
3. Then try sharing a trip again