This really seams like a remote problem but without another remote or TIU to test either of your devices against, this gets pretty hard to troubleshoot. Before resetting the Remote or TIU let's look at a couple of things.
What is the signal level of your engines when your engines on your layout and on the test track?
In MENU -> SYSTEM -> TIU --- make sure that there are 4 available TIU addresses you can add (assuming you only have one). If not, your remote may be looking for a TIU that doesn't exist.