Hello,
after you turn the key on, does the main contactor close?
(You should hear a pretty good clack sound).

If it doesn't close, the machine will obviously not power up.
Then you should check the emergency stop buttons circuit.

Check the white connectors on the back side of service panel also.
There is often a problem with contact there or the connectors are slightly disconnected.

You should also check is the control switch on service panel. It should be turned "platform" (not to "base").

It's absolutely normal that your brake release works. This is system that overrides any electronics. The power is directly supplied from batteries to brakes electric magnet coils.

Tell us how you're doing...