Unable to upload texture packs to Realms

When I try to upload the Festive Mash-Up texture pack to my Realm (Or any texture pack, for that matter), it says that it successfully uploaded the pack, but when I go into the Realm, there is no texture pack. Occasionally, a pop-up saying “Some of the selected content could not be applied” appears. Additionally, when I try to do this, none of the Realm members are able to enter.