mesa 7196s ethernet cable

No it does not, even a 30 meter long cheap cable works, for a Plasma that does huge amounts of interference!
So, what does
ip a
in a terminal return?
Did you set the jumpers on the 7i96S for 10.10.10.10 as stated in the manual?
If possible, make sure the 5V supplied to Mesa board is actually measuring 5V, plenty small power supplies have lover voltage causing issues.
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Since the LED's on the board react to ping, cable should be OK, but if the cable is DIY i would change it jus to be sure till everything is set up and working.