Have you entered a qualified persons as a dependent on your tax return? If not, you are not eligible for Head of Household.
See this TurboTax support FAQ for HOH - https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-filing-status/qualify-head-household...
Qualifying Person - https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-filing-status/qualifying-person-head...
