Cannot sign into Government Gateway to access personal tax account

I am a Crown Servant posted overseas and file a self assessment return online in order to pay tax on a small amount of income I receive from renting my property while I'm abroad. I have a Government Gateway account but I cannot seem to use it to access my personal tax account and file my return as after entering my Government Gateway ID and password, I'm taken to a screen that asks me to enter an access code from the Digidentity app. Since Digidentity no longer supports Government Gateway due to HMRC's decision to withdraw the Verify UK service, this effectively means I am locked out of my personal tax account. I have followed the instructions posted elsewhere on this forum to click the 'You can get help' link underneath the access code request, but selecting 'Change how I get my access code' on the following screen just takes me to a 'Sorry, we're experiencing technical difficulties' page which asks me to try again later. I cannot fathom how on earth I'm meant to access my tax account given that I get stuck in this loop every single time.

Hi carolinejq,

If the system does not take you to the process of resetting how you get the code, you will need to contact our Online Services Helpdesk

Technical support with HMRC online services

Thank you.