Can't Download Books onto IPad from IBooks

A couple of weeks ago, I started experiencing an issue with IBooks and not being able to download my purchases onto my IPad Mini 4. In the Store, when I click on a book to purchase, I get a little spinning circle and nothing else; or it shows the purchase going through, but the book doesn't show up in my Library or as a recently purchased book. At the User Forum's suggestion, after trying all the other recommended fixes (signing in and out of my account, etc), I updated my system to v11.2.5 as suggested, which worked initially for a couple of purchases I made last week; but today an experiencing the same problem as before. Is it just me or is once Reliable Apple rife with glitches of late? My other recent development is that I can no longer sync my IPad with my Desktop, and again despite all the recommended user-suggested fixes, a big fat NADA. Ready to jump to android platform and ditch Apple altogether. Somebody, please help as getting an actual Apple Tech on the phone is also impossible. Thanx