I need cab light help. Problem fixed with engine reset

Try resetting it by following the procedure on page 19 of the manual.

Reprogramming your locomotive to restore features If your locomotive is unresponsive to your commands in the TrainMaster Command Control
environment, we recommend that you follow this procedure to reset your locomotive. All factory default settings will be restored when you reprogram the locomotive.
1. Slide the Command reverse unit switch to the PROG position.
2. Plug in and connect your Command Base.
3. Place your locomotive and tender on the track, then power up the track.
4. Press ENG and enter the locomotive’s ID#.
5. Press SET.
6. Press ENGand enter the locomotive’s ID# again.
7. Press AUX1.
8. Enter 1for this particular locomotive.
9. Turn off track power and wait ten seconds.
10. Slide the Command reverse unit switch back to the RUN position.

At this point, your locomotive has been reset. Restore power to the track and operate the
locomotive as usual. Be sure to use the ID# entered in Step 4

The reset should do it, the cab light thinks it's a strobe, it's driven from the R4LC smoke/feature output.

Attempting reset, No joy.  Following instructions on pp.19, of the 844 manual, I begin the steps on the cab2 remote, but each time I get to the press "aux1" step 8, the screen changes to the "run" icons.  Therefore I can't enter a "1" as required to finish the reset.  So of course it doesn't take. Further, pressing the "R" reset button on the cab 2 gives me toot, toot,...toot.  Still a blinking cab led 

Ted, just press the key that corresponds to the 1, that would be the upper left hand key.  The keypad icons change, but it'll still recognize the numbers.

 That did it!  Thank you Marty and GRJ. I wonder if the millenials have these kinds of problems.