Uc to lcw to lcwra

Hi I recently was assessed to have lcwra last month, I first handed my sickness note in november 2022, I was on uc, I continued to put sick notes in, then I had a phone assessment and was placed in lcw group, about 16 months ago I received a review pack which I completed and sent back only to be told there was a massive backlog, I received a letter about 2 and half months ago to go to assessment which I was put in the lcwra group, last month's payment was around 800 which I received, today I was told I won't be getting backpay as nothink owed, is this right please and what should I do now thankyou