Well, this seems very simple to me.
As others have stated above, the delinquent taxes are a 1st lien on the property.
This is an obvious exception to title missed by the title co. and should be explicitly covered in the title ins. policy.
You have a clear claim with the Title Co. under the ins. they issued! File your claim under the guidelines outlined in the policy.
Maybe my aging mind is missing something, but I think this is a simple title ins. claim. Or does everyone have me on ignore.
Best,
Kurt