Make sure that you selected the IR light in the OXO Core lighting control.
OXO Core has a hibernation mode that activates when any of the lights have been on for more than 15 minutes. It is therefore necessary to check not only that the IR light has been selected but also that it has not entered hibernation mode.
To turn the IR light back on once the OXO Core has entered hibernation mode, you only need to move the lighting control to another position and select the IR position again.
Additionally, you should check that there is not excessive light in your dental cabinet.