1756-L55 (V16), I/O blink, no splats.

I have a client who has a 1756-L55Mxx running V16.xx, in a 4-slot chassis.
The chassis has:
-DNB devicenet scanner
-M04SE motion module
-L55 processor
-ENBT Ethernet card. (connected devices unknown beyond a PC-based HMI...no E/IP devices shown on I/O project view)

Viewing the project online, there are no yellow SPLATS in the I/O string. The controlled machine works without reported errors.

I suspect that there's something amiss in their the DeviceNet or Motion module.

Is there something else I should look for, and some way to find them?