Backing Up iPad

I'm trying to backup my iPad to see if ANOTHER PROBLEM I'M HAVING can be resolved by resetting my iPad.

Apple Music crashes every time I open it so, after having zero success here asking "Why is my Apple Music App Crashing?" I've taken (or at least, tried to) matters into my own hands.

I thought I'd just back up my iPad to my computer and then erase it and restore it. Well, not so simple apparently.

NOTE: I've been an Apple user since 1984. I've sworn by Apple and promoted Apple every chance I could but . . . my patience is now wearing very thin and am feeling deceived.

Anyway, when I try to back up my iPad to my iMac (High Sierra 10.13.3) I get the following message (see pic).

I then "Authorize My Computer" to which I get a message saying "This computer has already been authorized".

I've attempted this a couple of times now and am just feeling like an idiot.

I've been promoted on my iPad with a verification code. I've entered it and still, no go.

I'll never become a Windows User but gawd . . . I find myself wishing there was an alternative to Apple these days.

Help me NOT feel this way. Please!

And then . . . I try to post my problem here and get THIS FEEDBACK!