LIS communication

We have 2 MGC240s and they are currently linked using QuickLabs LIS.  We have been trying to break that connection in favor of interfacing directly with our LIS, through a DI interface.

I made all the setting adjustments needed, as described in their bi-direction communication specification, but received "run time error 6: overflow" when attempting to send data to our system.

Any ideas on how to make the connection successful?