Today I realized that I was using the old android app, so I uninstalled it and installed the latest version here:
https://play.google.com/store/apps/details?id=piuk.blockchain.androidI also decided, finally, to create a phone-only blockchain.info wallet and pair that account with my phone. This account has only a fraction of a bitcoin.
In the processing of attempting to pair my phone with the new wallet, blockchain.info gives you two QR codes to scan from. The first is for the latest app version, and the second is for the older version. I had the latest version, so I scanned the QR code that was marked as being for the latest version. Yet, each time I tried, I would get the error message "Failed to decrypt wallet." I figured maybe it was due to my wallet being new. So I would wait and try again. All totalled, I tried pairing about a dozen times, each failing.
Finally, I decided to scan the other QR code. The one that is marked for the older android app. First try, it worked. What the hell?