Alternatively, the printers also have a wifi card, that enable me to connect fine with an IP and with port I can specify (currently 8686), but even in MC network mode, it reports it can't open the port.

@larsbrubaker

Some progress:

Yes, same port. In my case Com port 3 and baud is 115200

Then I find that MC was set to a networking printer. I disabled that and it appears to connect now via com 3, but when I try to communicate with printer, even homing the motion, there is no response.

However, sometimes it will begin to accept a command, but up to a 30 seconds delay. Then the homing will engage.

I tried other USB ports and all baud rates without success.

It connects fine and controls properly with Simplify3D, Lerdge software, and Cura, just not with MatterControl so it's distinctive to this app.

We have a few MP Delta Pro's that we would like to use with Mattercontrol via USB. There is a built in profile for these printers, but it wont connect. The com port is visible, but times-out on connect attempt.

Some of these printers are stock, and a few have been upgraded to newest Lerdge firmware, but the issue remains. Any ideas? I see in the printer connection options there is am IP address box. Perhaps the default numbers are incorrect.