This is the link to post in 2017 from another user (oops Xamarin does not allow me to post a link so please search up this topic: Quite simply the worst development experience I've ever had...). Well, the subject says it all. If you do find it read it. I am having a similar level of frustrations with seemingly random issues in using Xamarin. I have been trying Xamarin on-off for many years but failed to get a stable development environment. Every time I failed, I attributed it to my lack of understanding. The simple and basic things stopped you in your track.
In the latest version of everything, I start a basic project. There is nothing in it. It only has the code that VS starts with. I build and try to deploy it. It turned into a nightmare of three days. I was not able to run an emulator for android. I eventually gave up using the emulator. Fair enough there are other security-related issues or Android dependencies that are preventing the emulator to work. So I used my android phone to deploy the app via USB and it worked. BTW, they QR code to run live play is another issue with Xamarin. In any event, I finally thought the worst was over. I added a button and build. Nope, it won't build. Many errors showed up and things just errored out from FileNotFoud exceptions to zillion other reference issues. So I was thinking that I may be rushing into putting a button on the page. Let's start a new project and make sure development environment still works. Guess what, it won't even work with the basic new project with default files in the new project. I could not build the project. This is incredibly frustrating.