Glad you are running again at least.
All I can suggest is double check your pins when re-connect your hardware and make sure they don't conflict with anything the MKR may need in regards serial pins.
Maybe also try the RTCZERO on its own without any hardware too.
Or maybe another RTC library ?
And once again do check the older MKR section (marked as read only) as there are some great posts by those who tested this thing. Also take a wander across to the hackster.io website as they have quite a bit of MKR projects you may be able to get extra info from.