Hello Arlorean!
There was an issue with our 7.3.0 Unity SDK release but (only happening for the Unity Asset store, not from regular git installation).
There are two approaches to solve this:
- Update to 7.3.1, which received a hotfix
- Manually install glTFast and Newtonsoft plugins.
If you were to update from a previous version to this broken 7.3.0 version, you would see no errors because the dependencies should already be installed, but if 7.3.0 was your first install, you should update to 7.3.1 or install those plugins manually.