Asking me for agreement of terms and conditions but when I agree it won't install anything

Hi, Jayjay!

After reading your post, I see that you've accepted the iTunes and App Store terms and conditions, however you're still unable to make purchases in the iTunes and App Store and are still getting the alert to accept the terms. I'd be happy to help!

Based on what's going on, I'd recommend using the following steps to troubleshoot:

1. Force close all open apps, particularly the ones that may request access to the iTunes and App Stores: iTunes Store, App Store, iBooks, and Music apps: How to force an app to close on your iPhone, iPad, or iPod touch - Apple Support. Then, restart your iPhone: Restart your iPhone, iPad, or iPod touch - Apple Support.
2. See if the terms and conditions continue to pop up. You may have to accept them one more time, but should no longer appear.
3. If the terms and conditions do continue to appear, try another network. If you're using cellular data, try on Wi-Fi. If you're already on Wi-Fi, see if it continues on cellular or a different Wi-Fi network.
4. Check the terms and conditions again.
5. If you still get the repeat pop up to accept, check for (then install) any available updates for the iOS software: Update your iPhone, iPad, or iPod touch - Apple Support.

Cheers!