Reactivating Self-Assessment after a long break (over 20 years)

I last submitted a tax return for the 2002 to 2003 tax, after which I was taken out of Self -Assessment. I now find myself needing to submit a return for the 2023 to 2024 tax year for my investment income. I have no other reason to submit a return. I submitted form SA1 a couple of months ago, but this was rejected, as I already have a UTR . I can see my Self-Assessment details for the old years in my Personal Tax Account. I have read in other posts that I will need to reactivate the account, but none of the instructions have been very clear on how this is done. I have logged into my account recently, so is this all that is needed? I had thought I would need to receive a notice to file from HMRC before submitting a return for the 2024 to 2024 tax year. However, do I simply submit an unsolicited return online for the 2023 to 2024 tax year sometime between 6 April 2024 and 31 January 2025? Your advice would be appreciated.

Hi Mitre64,
You can send an unsolicited return, though to ensure that your return is processed as quickly as possible, it may be better to confirm that your Self Assessment record has been reopened, and a return is expected for the year.
If your previous SA1 submission was rejected, contact us by webchat or phone here:
Self Assessment: general enquiries
We can review your record, and issue the notice to file if necessary.
Thank you.