Powering MKR WIFI 1010 with Vin

I am trying to power the MKR Wifi 1010 board using the Vin pin using a lipo battery. When I supply power to the board using Vin the led on the board turns on but the program doesn't start running (to debug I just have it trying to turn on an external LED when it powers up).

First thought was that the battery isn't supplying enough current but not sure. I know the specs say minimum 1024mAh, 3.7v lipo battery is supported, but I'm not sure if this is just for the battery port on the board or applies to the Vin pin as well. I am currently using a 2000mAh, 3.7v lipo battery and it isnt working.

I have double checked my code and there isn't any "while (!Serial)" statements that would be causing this, for example.

Thanks in advance for any advice.