Find accessibility issues
In the upper-right corner of Power Apps Studio, select the icon for the App checker.
App checker icon.
In the menu that appears, select Accessibility.
A list of issues appears, sorted first by severity and then by screen.
Select the arrow next to an item to show details about it.
Accessibility checker details.
Select the back arrow to return to the list of items.
If you decide to address an issue, select it to open the affected property.
After you change one or more properties, select Re-check to update the list of issues.
Resolved items disappear from the list, and new items may appear.
Reference:
https://docs.microsoft.com/en-us/powerapps/maker/canvas-apps/accessibility-checker
https://support.microsoft.com/en-us/accessibility/enterprise-answer-desk