The TurboTax accuracy guarantee essentially covers calculation errors such that Intuit will pay you penalty and interest if you have to pay an IRS or state penalty or interest because of the calculation error.
Intuit will not, however, pay any amount of actual tax that was due.
IF it is the Portland OR, "Arts Education and Access Income Tax (Arts Tax)"
.....I don't see that Oregon includes that City tax in their state forms.
.....TTX does work with a few City forms in a couple other states, but Portland would have to establish communications with, and form preparation with, ALL of the tax software providers if they (Portland) wanted to receive the Arts tax thru any of the yearly personal income tax returns. Apparently, they have not done so.
Someone else may have more detailed information, but from what I see, it must be paid separately from your Fed&OR income tax returns, either Online at the Portland tax website, or on paper using their downloadable forms.
Perhaps talk to some long-time Portland resident.....a neighbor or at-work for details about how this is really supposed to be paid.
As SteamTrain noted, the Portland Arts tax is not a state tax; therefore it is not part of the Oregon state income tax return (see https://www.oregon.gov/DOR/forms/FormsPubs/publication-or-17_101-431_2018.pdf). In fact, the Arts tax is not an income tax at all, although it is levied only on Portland residents who have a certain amount of income.
TurboTax generally helps you calculate income taxes, not property taxes or any number of other taxes that local governments may assess. As SteamTrain noted, in practice it would be impossible for TurboTax or any tax software to handle the entire universe of local, non-income taxes that are levied across the US.
Therefore, TurboTax was correct in saying (if it said it in those exact words) that all your state taxes were done, because your state income return was indeed done.