Aggregating Snapchat content is a bit different than other social content. Per usual, only public facing content is accessible via Snapchat, but, in addition it must also include a tagged location, as direct links can only be found via https://map.snapchat.com/.
Once the desired content is located on the map, you will need to click the Share button to copy the direct link to the Snap:
Once the direct URL is acquired, you can manually aggregate the Snap via the Create Tile section of your stack.
For any further questions or queries, please submit a request and our support team will get back to you.