Can I ask you to confirm if you are still seeing a blank for the ‘Last Weather Call’ (note, I am not asking about ‘Last Successful Weather Call’)? The only thing I can think of that would explain an invalid Last Weather Call time stamp is either your controller is not connected to router, or your controller is in remote controller mode:
https://github.com/OpenSprinkler/OpenSprinkler-Firmware/blob/master/main.cpp#L722
in all other cases, it would at least have a valid Last Weather Call time stamp (even if that call turns out to be unsuccessful in the end).