Can't access one of two app accounts

I have two accounts, one which I use all the time and no problems. Apparently, I did not set up an authenticator app to use with the other one and now I can’t access it. I have a bulb for which I had set up a schedule and while I can use this bulb through the one app, I can’t access the schedule I set up on the other account.

So how do I get into that app?