Our 2004 has set for a while, maybe 5 months. The transmission will not engage. on 2004 Dodge Sprinter 2500

Nothing happens after starting and putting in drive or reverse. Could this be just a simple TCM replacement?

Asked by for the 2004 Dodge Sprinter 2500
Are there any type of warning light(s) on (check engine/service engine soon)? Did you check the fluid level in the transmission?
No warning lights. It is actually my partner's in our tax office. She has told me that it did not come with a transmission dipstick, that was an option, they did not get! They male of the couple added a quart of fluid. She is ordering a dipstick, since the Express van now has 160,000 miles! I was going to see if it had an OBD II port and check the diagnostics, but, she never brings the key with her. But, she thinks because it is an "electronic transmission" that could be the problem. So I thought I might see if the TCM could just shutdown.

Many bad habits and little maintenance. Always the root of the problem, right? Thanks for any ideas.