modify relationship cheat only works on certain target sims. Help!

I have searched online but haven not found a solution to this problem yet. I have tried it on a few different Target Sims with LTR_Friendship/Romance and it works on some but it doesn't work on the target sims I would like it to work on. 

The current Sim I am playing I have moved out from the original household because his parents died of old age so he is now living on his own and I wanted him to try and establish a relationship, but it wasn't going well, so I wanted to give him a boost. I never had any issues with the cheat before until this character. I tried it on his childhood friend (LTR_Friendship) and that worked fine, and I eventually tried it on the landlord the same way, no issues there. But when I tried it on someone he met in his childhood home, it didn't work. Even someone new, in the same age group (young adult) I tried LTR_Romance on a different Sim just to see if it was just that was didn't work, but that was fine. I'm wondering if it's just those Sims I can't cheat 🤔

I know it's not a young adult issue because I've played young adults and have had no issues before.