There is a file 2A3A8A6D6826EF6CC653030E7D695C41.zip in the folder C:\Users\[User Name]\AppData\Local\Xamarin\zips that downloads the first time you compile a Xamarin forms android app. If this file does not download properly you get 55 errors about missing resources on the android project. Deleting the file from the folder will cause it to download again when compiling which resolves the resource missing errors. The file size at the time of this posting should be 220K some people with the issue had a file size of about 16K
It would be nice if Xamarin had a better notification if this file does not download properly.