I set up the unity package for this project as well as the sample project within my VR project for the Quest 2. After fixing all the errors I built it to my device and set it to call OnSignIn() on Start(). There were no errors and through debug logs I noticed that although this line of code is run, the program never actually makes it to OnAuthenticationFinished().
GoogleSignIn.DefaultInstance.SignIn().ContinueWith(OnAuthenticationFinished);

Although OnSignIn is called during start, there is no popup for google login or anything like that.