Ugh, problems with both trikes… Sorry to hear that! I have a spare parts bike that I raid (frequently) to supply needed parts to my running bike.
I didn’t realize that it was only operational for a tiny bit. That is very peculiar. Can you look at the battery pack and see if it has fuses that you can access? If so, that’s a possibility too. Finally, does the battery itself have an on/off switch? And, can you tell if you switch it off and on whether it’s turning on? Mine has a power display so I can tell. If it’s just dead (and it’s supposed to have a gauge or something) then it’s still probably the battery that’s at fault.