Okay, so in Skyrim: Special Edition on my PS4 I became a vampire lord a while ago but recently I decided to be cured. I wound up wanting to do quests for people in Castle Volkihar, so I had Serana turn me into a vampire lord again, which she did but everyone there was scolding me about coming back to the castle as a human even though I still have the power to become one. I decided to have Falion cure me and then become one again to maybe fix the problem but he doesn’t give me the option to do so. It all happened randomly. I had done a mission for Fura Bloodmouth but then whenever I had come to tell her it had been taken care of (I had done nothing in between doing the mission and coming back). I have access to PS4 mods if there are any that could fix the problem.
This appears to be a bug. Unfortunately it seems only fixable via a console hack. Since you are on the PS4, I don't think anything can be done apart from reloading an earlier save before you were cured. Since you say you only decided to be cured "recently", hopefully it won't take too long to get back to where you are now.