Slow, or no, internet connection can delay the GIF delivery process.
With the app open, triple-tap the bottom right-corner of the iPad. You will get the App Status pop-up on screen. The App Status window provides an overview to let you know if there are still GIFs to be sent, which will explain any delay.
Thanks to our offline queue, the booth will continue to work, and the attendees will receive their images once the booth connects to a strong internet connection.
(Disclaimer: Your booth must be connected to the internet prior to any delay or drop in internet connection in order for offline mode work.)