Can't file tax return online

I have registered and received post from HMRC telling me to complete tax return. The post also give me my UTR and confirming they have set up a self assessment record for me. However, when I sign in to https://www.gov.uk/log-in-file-self-assessment-tax-return , I cannot find any button in the page to file tax return. Have I done something wrong or do I have to wait some more time?

Hi,

After logging into your personal tax account through the Government Gateway, you should be able to file your return by clicking on the Self Assessment tile on your personal tax account's homepage. If the Self Assessment tile is not present, you will need to contact our online services team.

Technical support with HMRC online services

Thank you.