Income Tax Refund due confirmed but no way to claim it

When I log into my Personal Tax Gateway account the screen clearly says I am owed a tax refund. But it then says I CANT claim it online. I follow the help links to find out how I CAN claim it and just get stuck in a loop driven by the online assistant who directs back to the link I used to get to the online assistant in the first place. There's no doubt I'm owed the refund, that is clear on the screen. But I have no way of getting it. Tried calling but I don't get passed the recorded prompts that eventually tell me to check the advice online. And round we go again. So the simple question is - if my refund is confirmed but I cant claim it online, how do I claim it? Surely that's an answer that should appear at the top of any FAQ list?

Hi,
If you're unable to claim your repayment by phone, webchat or your Personal Tax Account, you can claim your repayment in writing.
You can find the address to write to, as well as our webchat link and contact number, here - Self Assessment: general enquiries
Thank you.