HELP Power button flashes then nothing

I was riding at cruising speed then the board shut off and got disconnected from my remote.

When trying to power the board back on the red ring on the power button flashes then nothing.

Any idea what’s going on or how to troubleshoot? Manufacturer says to buy a new battery.

Start by testing the battery voltage. If you don’t have a cheap multimeter get one. Any cheap one will due so no need to spend more than $20 or so. Test the voltage at the battery connector