update installed but not appearing on pick a boom

I just installed the Easter theme but it is not appearing on the Pick a Boom holiday pack. I also received a message that Firefox could not install my update and to check and see if there were any other versions running on my computer. After reinstalling and restarting my computer, and verifying that there is only one version on my computer, I still can not get the new Easter theme. The St. Patrick's Day and Valentine's Day came through ok after installing the Holiday Pack at Christmastime. Any help? Thank you.