Digi Ehtherlite 2 - Cannot communicate with the serial side computer.

Digi Etherlite 2 (PN: 50000989-01 N). The Digi box is used to connect two computers. The Digi box has been working fine for the past 5 years. Now, on the Digi box the power light and the link light are solid and I can ping it from the host server network. But the link on the serial link seems to be broken … communication is not occuring. I’ve reset the Digi box with no results. Is there anything else we can do to test if it’s the Digi box that needs replacement??