You really should NOT be using iMazing for Apple iOS/iPadOS upgrades/updates.
That stated, you should check to make sure you are using the latest version of iMazing.
You SHOULD be using Mac or Windows PC, either using the Finder on a Mac that has the newest macOS Catalina, or later macOS, installed OR with an older Mac with an older Mac OS, download and install the latest iTunes version ( or latest iTunes for Windows PC ), make sure the Mac or Windows PC is connected to the Internet, connect your iPad by the USB charge cable to the computer and let the iTunes application upgrade/update that iPad model, using the iTunes Software Update feature, to its current, maximum OS of iPadOS 15.7.1 or iPadOS 16.1
Make sure your iPad is, at least, charged to 50% or greater to attempt this.
Also, make sure your iPad has, at least, between 6-8 GBs of free internal data storage space for downloading and installing a major iOS/iPadOS upgrade.
Make sure your desktop/laptop computer has plenty of internal drive storage space, also.
Also, make sure to do a backup of your iPad's data, prior to upgrading/updating.
Backup to Apple iCloud and/or a full Mac or Windows PC using the same iTunes app OR, if a newer Mac running macOS Catalina, or later, making a backup using the macOS Finder app.
Tap the Apple support links below.
How to back up your iPhone, iPad, and iPod touch - Apple Support
Restore your iPhone, iPad, or iPod to factory settings - Apple Support
Restore your iPhone, iPad, or iPod touch in iTunes on PC - Apple Support
If you can't update or restore your iPad - Apple Support
Best of Luck to You!