Evolve Baboo Gt Bms problem

Hi, I have a problem with my Evolve Bamboo GT—it won’t turn on. I measured the voltage directly on the battery, and it shows 41.3V, but when I measure the voltage at the BMS output (P-), it only shows 18.6V.
Could this mean the BMS is faulty?
The battery is fine I made it last year, and everything has been working until now.

I have disconnected the cables to the motor controller.
I need to find out whether the output voltage from the BMS should be the same as the input voltage. (When measuring with B-, I get 41.3V, but when measuring with P-, I get 18.6V.)
I’m not sure if the issue is with the BMS or the motor controller.
I would need to find out if the battery with the BMS connected, but disconnected from the motor controller, shows the same values on the output of the BMS as on the input
Thank you very much for your help!