I was using my phone to imessage and now it just says " waiting for activation" and I don't know how to get it working again. It keeps saying "an error occurred during activation" try again.
There may be a problem on Apple's end or you are experiencing internet issues with your ISP. Just give it time to sort itself out. If after about an hour or so, reboot your iPhone or disable iMessage for a few seconds then re-enable it to see if it activates.