iPhone won’t go to sleep when using kindle app

Hey there sly53,

Thanks for reaching out to Apple Support Communities. I understand your iPhone will not auto lock when expected while using the Kindle app. I’ll be happy to help.

Go to Settings > Display & Brightness > Auto-Lock and make sure that is set to the correct time. If it is, force close the Kindle app, restart your iPhone and see if this helps.

How to force an app to close on your iPhone, iPad, or iPod touch

Restart your iPhone, iPad, or iPod touch

If the issue continues past that, check for an update to the Kindle app and your iPhone. This can further isolate the cause. Remember to back up your iPhone before updating as well:

How to back up your iPhone, iPad, and iPod touch

Update your iPhone, iPad, or iPod touch

This link can guide you on updating the Kindle app:

Update apps or use automatic downloads

If that doesn’t resolve this, delete the Kindle app from your iPhone, restart, and install the app. See if the issue is resolved.

Cheers.