Paying Trust Tax by direct debit

I don't know if any body else has this problem. I am trying to set up a direct debit to pay  self assessment tax for a family trust I run. I log in to my online account click direct debit and it asks me to sign in again. I do that and just get back to the log in page. web chat suggested to avoid this looping, I clear the browsing history, clear cookies and try again entering the user ID & password from the keyboard (instead of using autocomplete).

I have done all this and have tried three different browsers. Still the same answer for both small trusts I run. Direct debit works fine for my individual tax. I may end up just posting a cheque now they have discontinued the post office payment method.