There are times when a theme prompts for an upgrade to an accessible theme, but even after the upgrade, the theme still prompts that it needs to be updated. This rarely happens and usually occurs in very old themes. Upgrading a very old theme will require a few additional steps.
Upgrade to an accessible theme
Go to the Theme Editor
Select the Theme that you're having trouble upgrading, and click the Edit button
Scroll down the sidebar to the bottom and expand Legacy Variables
Set Text backwards compatibility to False
Upgrade the theme and click Publish
The theme upgrade is often required to access accessibility features. For more context, see the guide to accessibility features in Zoomforth.