ml1100 msg with plc5/20E Rev J

I need to make a PLC5/20E communicate over Ethernet with an ML1100. I have the option to place the MSG in either PLC but I can't get either side to work completely.

I can make the ML1100 write to the PLC5...but not Read From it
I can make the PLC5 Read from the ML1100 but not Write to it

So I'm only able to get data to flow in one direction. The data in the PLC5 can't be written to the ML100.

What am I missing?

Let me add to this... the PLC shows its a Rev J which should support CIP, but RSLinx doesn't show it in the ETH-I/P driver
I had to add it manually to the ETH driver.
. . . I'm thinking that's significant.

Success... somewhat

OK I have one more update. I have the ML1100 reading and writing to the PLC-5.

BUT!. . .

It wont work after any transition from program to running. I sequence them like I always do but upon entering run mode, both MSG go EN in sequence and will never go DN.

If I disable the rungs of the MSG for a while (90 seconds maybe, I'm still seeing if there is a specific duration needed) after switching to run mode, both MSG eventually go ER. If I then I enable the rung, they take off and work great. I have them talking every 50 ms without a problem... once they start.

What setup is needed to prevent this? I wasn't aware that MSG took this much care and feeding .