Cannot read some library books on Kobo Aura H2O and Kobo Libra 2

Like thousands of others, I get the "Your eReader is not authorized to open this book" even though it opens other books checked out via Overdrive. I've gone through dozens of deauthorizations of computer and Kobo but cannot seem to fix the problem. My purchase of the Kobo Libra 2 was in part a hope that the problem might go away, but it didn't. I'm using a Mac running OS 11 so I cannot revert to ADE 3. Thanks for any help.