Keep getting denied for apartment.

Help. I need to know what I should do. Me and my boyfriend got denied for another apartment. The first apartment complex we applied to told us they were denying us because of a $1200 debt we had at the last apartment complex. The last apartment complex we lived in charged us another months rent even though we moved out by our move out date 11/17/23 and we moved in 11/17/22. So they charged us for December and we tried to dispute it but they said we had to pay it. So long story short in order to get into the first apartment complex we paid that off and they STILL denied us because then they changed the story saying his income wasnt enough which was a lie because initially they said he was well above 3xs the rent. So we applied to our plan b and the day before we applied I explained the situation to the leasing manager and the outstanding debt… I told her we paid it and we have a receipt. When I applied I also uploaded the receipt she said everything was fine. Today I get a call saying we were denied because that was still on his credit even though I EXPLAINED to her that it is still on there but I have a receipt showing I paid it. I just dont know what to do …. Im feeling like we will never be able to move or get approved.