Activate Theme ERROR

Hello, I recently updated 4.5.5. Although the site is working fine and in the WP themes it indicates 4.5.5 is installed, it is requesting that I "activate" the theme, when I enter the registration code, it says activation failed. The registration is valid, so what is the problem? Also, I checked the change logs and the last couple of updates have been few and far between and their substance is nominal offering no site improvements that I can see. Please clarify if you are still supporting the theme and if you intend to make any material upgrades in the future. Thank you