Hello, Jim. I waited a while to respond as I don’t have this combination running. I may have some questions to help troubleshoot, though.
What version of esp3d did you use?
For reference, there’s a forum thread about flashing an esp01 with the ESP3D v3
The SKR specific stuff would be of little help, but the ESP01 flashing notes worked for me to flash one of my ESP01s.
It’s a good bet that if you used the stock v1e RAMPS MPCNC firmware that it is not configured correctly to support ESP3D on a RAMPS AUX port. Maybe someone like @jeffeb3 has some insight about that.