Have you checked the sharing settings on your game? If you have created a game but neglected to set the character sheet at game creation, then the compendium might not be set properly. Make sure it is set to the 5e compendium (again, here I am assuming). Also, you say you are in the process of creating new tokens. Can you describe your process? It is entirely possible to delete the token a monster came in with, improperly set the new default and wind up with a default that has no token. Subsequent compendium drags would not restore the old artwork (to protect homebrew changes). You could test this by deleting all copies of a particular monster from the game (there might be only one copy, but it's good to check for dupes) and dragging in a fresh copy. Or drag in a monster you know does not already exist in your game. Or create a brand new game and drag in a monster manual token. Any of these tests would verify that you have an appropriate connection to your purchased material.