Call Pickup Group "Feature is Unavailable" Message

So today I was presented with a very simple yet difficult problem. A customer had a problem with their call pickup group. Any time they would try to pick up a call after seeing the visual alert it would say "Feature is Unavailable". After doing some research on the problem I came up empty handed with others having this same problem. I made a few test calls and GCallPickup and then dialing the ringing number worked yet CallPickup didn't. Perplexed, I had the customer go try another set of phones in another pickup group and everything worked as it should. Absolutely nothing was different between the two configurations other than a the pickup group number (obviously...). So after an hour or so of wasted time troubleshooting and checking everything I created an entirely new pickup group and assigned the phones to it and voila, everything worked. I then deleted the old pickup group and changed the new one back to the old one's name as well as it's number and guess what, everything worked. My only assumption as to why this randomly started to fail all of a sudden is a database issue and removing it while creating a new one was the only solution. No other settings like extension mobility were in play and certainly all of the settings were correct such as the CSS and partitions. Weird...but at least it is fixed. I highly doubt TAC would have an answer other than the solution I ultimately came up with.