Unexpected error occurred during Tax Calculation.

we are receiving above error when clicked on Calculate Tax button on AP Invoice Workbench for one invoice.

We recently uploaded a vertex rate file where the CO-500090000 county tax effective date was set to 9/30/2015 due to expiration of the rate, and the Invoice we received had the invoice date:30-SEP-2015 and GL Date:30-SEP-2015 the active flag is 'Y' in zx.zx_rates_b. from below screenshot you see that the tax_rate_code for 'STD' the percentage_rate is set to 0 and effective_from and effective_to date is something which is in current, and for 0.5 the effective_to is upto 9/30/2015. Not sure if the invoice date is within the effective from and to date of 0.5% why the tax is not calculating...