There are multiple generations of this kindle.
To make sure that you are told the correct version of kindle fire that the customer is using, please make sure that you get a picture from them showing the about information on their fire. Have them provide you with their system as well.
How to find out Amazon Fire tablet Generation and Model - Bing video
How to Find What Model Amazon Fire HD Tablet or Kindle you have - Bing video
Have them also send you a screenshot of the about information in the clickfree app menu.
The app (on amazon) https://www.amazon.com/ClearviewProductions-ClickFree/dp/B09KX5HH81/ref=sr_1_1?keywords=clickfree&qid=1675290724&s=mobile-apps&sr=1-1 is found with this link.
A customer must sign into amazon in order to find the download option for the app.
The clickfree app is not compatible with the 5th Generation – Amazon Fire HD 8. I have asked the development team if they can make this compatible.
The clickfree app is compatible with the 10th Generation- Amazon fire HD however.
Here is also a helpful link to discover the type of kindle you are dealing with:
How to Tell Which Amazon Fire Tablet You Have (alphr.com)