I have a qualifying person to claim And I paid for all expenses. Why am I only allowed to file single and not HOH?

[ee-ea]

See this info

https://turbotax.intuit.com/tax-tips/family/guide-to-filing-taxes-as-head-of-household/L4Nx6DYu9

[Hal_Al]

Describe your qualifying person.

Two common situations:

1. You are the non custodial parent and are claiming your child as a dependent, this year.  That child is not a qualifying person for HoH, because he/she does not live with you enough. 

2. You claim your girlfriend as a dependent.  She  is not a qualifying person for HoH, because she is not related

Otherwise, you have, most likely, answered something wrong in the interview.