"Apple ID is temporarily unavailable. Try again later."

I've been seeing threads about this issue pop up and just wanted to add to the troubleshooting solutions that have been offered. I had this issue with the iTunes app. None of the troubleshooting solutions worked for me. So I took a guess that maybe it was a payment issue and not an app or account issue. I actually lost my debit card a while ago and updated my card info by going into settings, tapping on my name at the top and selecting Payment & Shipping. What I didn't realize is that my old card info was still in my Apple Wallet. After I updated my Wallet to my new card info, I was able to make purchases in iTunes again. Go to settings, scroll til you find Wallet & Apple Pay and that's where you can delete old cards and add new ones. I'm not saying other troubleshooting solutions are incorrect, but if none of them work or you're still having issues, check your settings and make sure your payment info is consistent. I also figure this would have the same affect in in the App Store too.