You need to supply an idle animation for the default animation- also make sure the name you're supplying matches the name in the blockbench animation file.
If you're using the latest version of MCreator, and the latest snapshot of Geckolib, it's also worth noting some of Geckolib's syntax is a bit broken. If you want to do custom attack animations, flight animations, etc; you need to lock the element and fix a couple of things in Geckolib's code, but it is still possible. (I can give some examples if this is something you need.)
You need to supply an idle animation for the default animation- also make sure the name you're supplying matches the name in the blockbench animation file.
If you're using the latest version of MCreator, and the latest snapshot of Geckolib, it's also worth noting some of Geckolib's syntax is a bit broken. If you want to do custom attack animations, flight animations, etc; you need to lock the element and fix a couple of things in Geckolib's code, but it is still possible. (I can give some examples if this is something you need.)