Root Cause . The MEMBER_SUBSCRIPTION_START_FIRST_DAY_OF constant was set to Y (invalid) instead of m, 3m, or empty. This caused dol_time_plus_duree() to receive an invalid DateInterval format, triggering a PHP Fatal Error that stopped the contribution form from rendering.
okay, that could be handled more gracefully. I think you should go ahead and see if you can find a similar bug report here, and if not then make one
