In this situation, the iTunes can't recognize the firmware or the IPSW file is not matched with your device. You can restart your iPad and update iTunes to the latest version. Or download the right firmware file by visiting IPSW Downloader. Besides, you can also use the third-party iOS system recovery tool to fix this issue. Or you can directly go to the Apple store to seek suggestions.
Tiana1
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How about force quitting it and relaunching it? Or try to force restart your iOS device. Of course, you could use professional iOS repair tools such as TunesKit iOS System Recovery if you would like to. Finally, the most direct and fastest way is to contact the Apple center/store for help.