If your students are completing work and this is not showing on your Teacher Dashboard it could be for a couple of reasons:
They are using the wrong account. Make sure they are using the account linked to your class. You can check the username for this by heading to Manage > Students and selecting your class from the drop down menu. The username will be displayed here. More information on checking the account they are using can be found here.
They are using different devices. Children can use different devices to Doodle. If they are switching between devices they just need to make sure:
They have internet connection when working so that the work syncs to the server. If they need to Doodle offline, they just need to make sure they use the same device whilst offline and then when they do have internet connection login on this same device so that the work syncs through to our server.
If students are still having problems with work syncing/saving this help centre article is useful.