The class ImmViewer lives in a file called QuillViewer which causes an error
Possibly because of this all script references in the scene are broken
The project is missing the Packages and ProjectSettings directories which can cause many problems down the line
the .gitignore should be based on https://github.com/github/gitignore/blob/master/Unity.gitignore with the Unity paths adjusted to reflect the fact the Unity project isn't the root of the repo. (Actually - I would probably recommend splitting the Unity project out to it's own repo - it usually makes life a lot simpler)
Please note that the file name and the .cs script name are not the same - this cause an issue.
Rename the script file name to ImmViewer.cs (same as the script name)
Several issues: