Total income $21,841. My dad is a Senior, how come when I enter the medical expense of $2104.77 it does not increase his refund?

The Medical Expenses credit is non-refundable. So if you taxes owing are Zero, or you have a refund, then you would not get any of the credit. https://www.canada.ca/en/revenue-agency/services/forms-publications/publications/rc4065/medical-expe...