I think this might cover your answer; Does RSA work for any message M?. If it is not working, i.e. there might be two distinct messages that have the same ciphertext ( as one of the reasons) then the decryption is not possible, so RSA is not working for all message $M < N$. This is not the case.
– kelalakaMar 25 '22 at 20:33
Please indicate if this answers your question. In that case we might close the question as a dupe, in the safe knowledge that you might not have an original question, but that it is already in the little knowledgebase that is [se]..
– Maarten BodewesMar 27 '22 at 16:26