Can't update because "there are purchased items that have not been transferred" to my iTunes library.

Hey there mktgman,

Thanks for reaching out to the Apple Support Communities. If getting the alert that "There are purchased items that have not been transferred" when attempting to update your iPhone, give the steps below from the following resource a try that can help: Transfer iTunes Store purchases to your PC - Apple Support

Transfer iTunes Store purchases to your PC

You can transfer your iTunes Store purchases from your mobile device to any computer that’s authorized to play them.

1. In the iTunes app  on the PC you’re transferring items to, choose Account > Authorizations > Authorize This Computer, then click Authorize.

2. Connect your device to your computer.

3. Click Transfer Purchases in the window that appears, or choose File > Devices > Transfer Purchases from [device].

If still having issues after going through the steps above, give these additional steps a try that can help with troubleshooting this issue further: If your iPhone or iPad won't update - Apple Support

If there's not enough space to update

If there isn't enough space to download and install an update, the software on your device will try to make space. It will remove only app data that it can download again and doesn't remove or relocate any of your data. If your device still doesn't have enough space, you can use your computer to update your device.

If you can't connect your device to your computer, you can make room for the update by removing content and apps on your device that you don't use. Go to Settings > General > [Device name] Storage.

Learn more about the space your apps and content use.

Keep us updated on the results.

Take care!