To Everyone in this post currently having issues with older iPad 2 models and Activation Server issues.
This issue has mostly affected iPad 2 models with SIM cards with Cellular data service.
For any of you with a cellular iPad 2 model, try removing the SIM card from the SIM card tray, located on one of the long sides of the iPad ( you may need something small or pointy or the original SIM card tray tool that came with your Cellular service iPad 2 to open the tray ), remove the SIM card, try either a simple restart of your iPad 2 AND/OR try a hard reset of your iPad by holding down both the Home and sleep/wake buttons simultaneously until your iPad goes to black and restarts with Apple logo, then release the buttons.
Then, try re-activating your iPad 2 without the SIM card in the tray.
If successful, return the SIM card back into the tray.
Good Luck!