Here are some ideas:
I saw online that ViVI ebikes have LCD screens. Does it power up and show anything?
If so, could you take a picture?
There are 4 types of external sensors: Brakes, Throttle, Pedal Assist (Torgue), Speed/Gear.
If you break sensors show that you are breaking, then the motor won't engage.
Even if you have a functional throttle or pedal assist (PAS).
If your bike is using these, there is a reasonable chance taht rough handling can cause them to report false breaking.
Your display can show if you are breaking and disconnecting the sensors will also disable them.
Throttle can be configured to override Pedal Assist, however it might not be by default.
So unless it worked before, you might need to either change the configuration or get a working PAS.
Faulty PAS can only do one of two things: Send that you are not pedaling or that you are pedaling like a robot.
You should be affected only by the first: Controller can block throttle if no speed and no pedal strokes are detected.
Speed/Gear should not affect your scenario. Just mentioning it.
That is about as much I can help with blind.