State tax filing

It does exist so let's look at some possibilities.

1. Perhaps the CO Social Security income exclusion  not functioning properly is causing trouble. If you receive Social Security, you will want to sign up to be notified when that issue is corrected.
2. Verify your property tax has no senior exemption and your income is low enough.

 Income Qualified Senior Housing Income Tax Credit | CO DOR 

“Colorado seniors 65 years of age or older may qualify for the Income Qualified Senior Housing Income Tax Credit. Please read below carefully to determine if you qualify for the credit, and to calculate how much you qualify for. 

1. Is your date of birth (or your spouse's date of birth) December 31, 1960 or earlier?
   • Yes: Continue to step 2. 
   • No: Stop, you do not qualify for this credit.
2. Were you (or was your spouse) a full-year or part-year resident of Colorado?
   • Yes: Continue to step 3.
   • No: Stop, you do not qualify for this credit. 
3. Is your adjusted gross income (line 11 of your federal tax form 1040, 1040-SR, or 1040-NR) for this income tax year $75,000 / MFJ $125,000 or less?
   • Yes: Continue to step 4.
   • No: Stop, you do not qualify for this credit. 
4. Did you receive a partial property tax exemption for your primary residence under section 39-3-204 of the Colorado Revised Statutes (commonly known as the Senior Property Tax Exemption, Senior Homestead Exemption or Disabled Veteran Exemption) for the property tax year? The exemption should appear on your property tax statement from your county assessor. You may have been approved for the exemption by applying in a prior year. This exemption is generally allowed if one owner of a home is 65 years old as of January 1, and has occupied the home as a primary residence for at least 10 consecutive years.
   • No: You qualify for this income tax credit. Continue to step 5 in order to calculate the amount of credit you are eligible to receive. 
   • Yes: Stop, you do not qualify for this credit. “

The program will look up your federal filing status and adjusted gross income (AGI) in the Senior Housing Income Tax Credit table and select the corresponding credit value.
 

There is always the possibility of technical issues but I feel your problem lies with one or both of the above issues. I did see where this has been reported in the past and determined not to be an error.