TiVo remote seems to have changed settings

I have had a Roamio and a Premier in the same room for a year and I have been able to use the remote that came with the Roamio to control both units by covering the front panel of the unit not being used. I assume that it was using the IF function so if the unit not in use could not "see" the remote all was fine. This all worked great until today.
Suddenly the remote works with the Roamio with the face covered and even if I completely cover the front of the remote it is still able to control the Roamio BUT it is no longer able to control the Premiere!
Am I right to think that somehow the remote is now using RF in place of IF? If that is right how do I get the remote back to using IF?
Any input on this would be appreciated. Thanks