7i77 Servo Enable

The last suggestion by Chris@cnc is correct .
From the diagram, the inputs are sourcing type ie negative logic.

ENA0- => 37 (neg of PS)
ENA0+ => 3 (DI-0)

Ive found another picture in the manual that might help

This is my suggestion. I always do it like this.

Put power on pins com on pin 37, + on pin 36,

Coneect a relay to ouput pin and run pin 37 to one side of N.O relay and other side to pin 3.
That should enable your drive. I always use mesa boards like this and never had an issue.