Just documenting a solution to an error I came across for other poor souls that may encounter it.
The Error
I’m using my own personal google account to access the Google Play Developer Console. I have configured this personal account to have administrator access to a project that is owned by another account. One day, out of the blue, I started getting an error every time I tried to save something under the Game Services.
An unexpected error occurred. Please try again later. (4800403)
I’m not sure what changed and I’m fairly certain everything worked on both accounts before. The number 403 in the error suggested to me that it’s some kind of an authorization problem.
The solution
As a Google search gave no hits with the same error code, I contacted Google support. Their first suggestion was to check permmissions in both the Play Console and Google API Console. Indeed, adding my personal account also to the API console fixed the error.
(Under https://console.developers.google.com/iam-admin/projects I selected my project and added the other account with the permissions I needed.)