Generally the error messages shown with FB lead Ads connector may be due to wrong mapping or use of special characters etc.

Yet there could be at times an error message which only shows : 'There was an error please contact support' 

This upon a lot of investigation on the root cause, mentioned that it was shown because the user who configured the connector was not the Admin of the FB page that was getting integrated with LSQ.

In order to ensure such errors do not occur, we recommend the Admin of the FB page to do the configuration of the connector.