Make sure that your model is correctly selected and keyframed. Go to the file option and click on the export gltf/glb.
In the right side, open up the animation options. Make sure the animation section is checked. Then, make sure the "Group by NLA Track" is unchecked.
Why is my animation only playing one part of the animation?
If you have a file that has two different objects keyframed, it is possible that the "Group by NLA Track" is still selected. If this is the case, your export will have two or more animation tracks depending on how many objects are keyframed in the scene.