No Last name on Passport/ BRP - Unable to register with HMRC for tax account

Hi, I am unable to create an HMRC tax account. When I fill in my details - (First Name, Last Name, NINO), I get the message that my details do not match the information on record. I suspect it could be because in my passport my entire name is under 'Given Name' and there is nothing under 'Family Name/ Surname'. On my BRP, my entire name is in 1 single line. For creating the HMRC account, both first name and last name are mandatory. Please advise how to proceed.

Hi,

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