kindle reader for iPad

My wife and I both use Kindle Reader on our iPads. Yesterday, Kindle Reader stopped working on both of our iPads, The screen is frozen and will not respond to any taps. After trying multiple taps, the app may decide to close. We have tried deleting the app and reinstalling, but that does not solve the problem. Is Amazon having problems with their servers or do we have software/firmware issues? I am using an iPad Air 2 running iPadOS 15.6. I cannot open the Kindle app to find out what release it is. Suggestions?