Hi Brenmont,
Thanks for coming to Apple Support Communities for help today.
iCloud storage space shouldn't affect an iOS update. If you have low device storage, then it could prevent an update. Your iPhone 7 can only be updated to iOS 15.7.2.
This article has some steps that can help get the iPhone updated: If your iPhone or iPad won't update
"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."
If the issue isn't device storage, then sometimes removing an old update and redownloading the update will work.
"Remove and download the update again
If you still can't install the latest version of iOS or iPadOS, try downloading the update again:
- Go to Settings > General > [Device name] Storage.
- Find the update in the list of apps.
- Tap the update, then tap Delete Update.
- Go to Settings > General > Software Update and download the latest update.
If you don't see the update in the list of apps or if the issue happens again, you need to update your device with your computer:
Learn how to use recovery mode if your computer doesn't recognize your device or your screen is stuck on the Apple logo for several minutes without a progress bar."
Have a fantastic day!