My issue is now resolved.
iPad 2 wifi+3G 64GB now running iOS9.3.
I got the cannot activate issue most others are reporting here as well (see my previous post).
To resolve the issue I needed to go a full restore on my iPad. Reminder: the home and top buttons pressed together with the iPad plugged into the computer with iTunes.
The restore took about 2 hours but its all good now. It first wipes the iPad and then puts the OS on, then after that you can restore from a backup you have. As mine is backed up to my computer, I used the iTunes restore process. I expect the other process will work for iCloud backups/restores.
Some more details are here: Use iTunes on your Mac or PC to restore your iPhone, iPad, or iPod to factory settings - Apple Support
Good luck and I hope this helps others!