In a post on GitHub, one of the PoGo-UWP developers, "Kaankehh", stated:

Hey guys, Like you already know the PoGo app doesn't work. The reason for that is that Niantic updated their server. The update ruined the API, the requests are now cryptographically signed. The latest update was forced so the app could read it.

Does this mean that it is over? No, the makers of the API are looking in to this, it is not sure if they can fix it.

What do you say? Is it over in your opinion? Sadly, yes. I dont think that the API creators will be able to decrypt it and if they will be able to get it to work, Niantic will probably add more encryptions. This is probably one of the I don't know how many encryption they will add.

We have to wait till the API creators have more news, I will keep you updated.