FrankZappa

Here's a brief overview of my situation: I left the UK back in 2018 and started travelling from my savings. In early 2021, I started working freelance for clients in the to sustain my lifestyle - All of my clients are based in the USA I moved back to the UK in Mid 2022 and continued to work online. I completed the most recent 2022/2023 return without any problems. I have now noticed a £100 penalty in my account and a notice that I need to file a return for 2021/2022 I think I should be classified as a non resident for this year - Is this correct? Do I still need to file a return?