iPad Storage Says Full

Bransbow Said:

"iPad Storage Says Full: [...]You know how usually it will tell you which type of data is taking up storage? It doesn't do that for me, it's just a big gray bar.[...]"

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"Other" Storage is the Culprit:

The storage named "Other" is the grey bar. So, to clear that, this is what to perform: Clear Other storage on your iPhone or iPad" - Apple Support

If your internal storage is full, your only option is to manage the storage that you have - and delete unused Apps or unneeded data. 

These support pages should prove to be helpful:

About storage on your device and in iCloud – Apple Support

What's the difference between device storage and iCloud storage? – Apple Support

Manage your iCloud storage – Apple Support

How to check the storage on your iPhone, iPad and iPod touch – Apple Support

Clear Other storage on your iPhone or iPad - Apple Support

“Offloading” Apps can also be a helpful method of creating temporary space for a software update.

https://9to5mac.com/2020/01/21/how-to-offload-apps-in-ios-to-save-space-without-deleting-their-data/

I certainly did read your post - and, on the basis of experience, my reply intentionally made no assumptions. Perhaps it is you that hasn’t fully considered the reply…

The link highlighted in bold-text, Clear Other storage on your iPhone or iPad - Apple Support, is perhaps the most relevant to your issue…

Bransbow Said:

"iPad Storage Says Full: [...]You know how usually it will tell you which type of data is taking up storage? It doesn't do that for me, it's just a big gray bar.[...]"

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What to Try:

Here is a User Tip I authored. See if performing it is operable with your iPad: How to Clear "Other" in your iPhone's Storage - Use Backup - User Tip