Why can't Visual Studio find my assemblies? - macos

Question

I'm new to Visual Studio, but not to programming. I tried to open a project which someone else sent me, and there are lots of errors (they are all the same). Please see the image below:
When I tried to check the runtimes installed, I see this:
I know that Newtonsoft.Json is installed, because I can see it in the packages folder.
So far I have looked at:
Getting "type or namespace name could not be found" but everything seems ok?
But I can't figure out how to fix the problem, as I'm using VS after several years. What should I do ?
I am using Visual Studio for Mac Community edition, version 8.2.3 (build 16)
EDIT: More Information from about Visual Studio:
=== Visual Studio Community 2019 for Mac ===
Version 8.2.3 (build 16) Installation UUID:
024bbaaf-47dd-4755-982d-29b842a90ef4 GTK+ 2.24.23 (Raleigh theme)
Xamarin.Mac 5.14.0.85 (d16-2-fix-mac-updates / 86973979)
Package version: 600000319
=== Mono Framework MDK ===
Runtime: Mono 6.0.0.319 (2019-02/52203786470) (64-bit) Package
version: 600000319
=== NuGet ===
Version: 5.1.0.6013
=== .NET Core ===
Runtime: /usr/local/share/dotnet/dotnet Runtime Versions:
2.1.12
2.1.2 SDK: /usr/local/share/dotnet/sdk/2.1.701/Sdks SDK Versions:
2.1.701
2.1.302 MSBuild SDKs: /Library/Frameworks/Mono.framework/Versions/6.0.0/lib/mono/msbuild/Current/bin/Sdks
=== Xamarin.Profiler ===
Version: 1.6.11 Location: /Applications/Xamarin
Profiler.app/Contents/MacOS/Xamarin Profiler
=== Updater ===
Version: 11
=== Xamarin.Android ===
Version: 9.4.1.0 (Visual Studio Community) Commit:
xamarin-android/d16-2/ebd65c9 Android SDK:
/Users/morgoth/Library/Android/sdk Supported Android versions:
4.4 (API level 19)
5.0 (API level 21)
5.1 (API level 22)
6.0 (API level 23)
7.0 (API level 24)
7.1 (API level 25)
8.0 (API level 26)
8.1 (API level 27)
SDK Tools Version: 26.1.1 SDK Platform Tools Version: 29.0.1 SDK Build
Tools Version: 28.0.3
Build Information: Mono: mono/mono/2019-02#e6f5369c2d2 Java.Interop:
xamarin/java.interop/d16-2#d64ada5 LibZipSharp:
grendello/LibZipSharp/d16-2#caa0c74 LibZip:
nih-at/libzip/rel-1-5-1#b95cf3f ProGuard:
xamarin/proguard/master#905836d SQLite: xamarin/sqlite/3.27.1#8212a2d
Xamarin.Android Tools: xamarin/xamarin-android-tools/d16-2#6f6c969
=== Microsoft Mobile OpenJDK ===
Java SDK:
/Users/morgoth/Library/Developer/Xamarin/jdk/microsoft_dist_openjdk_1.8.0.25
1.8.0-25 Android Designer EPL code available here: https://github.com/xamarin/AndroidDesigner.EPL
=== Android Device Manager ===
Version: 1.2.0.60 Hash: 686c817 Branch: remotes/origin/d16-2 Build
date: 2019-08-07 15:49:58 UTC
=== Apple Developer Tools ===
Xcode 10.3 (14492.2) Build 10G8
=== Xamarin.Mac ===
Version: 5.14.0.114 (Visual Studio Community) Hash: c6691164 Branch:
d16-2 Build date: 2019-07-29 15:54:06-0400
=== Xamarin.iOS ===
Version: 12.14.0.114 (Visual Studio Community) Hash: c6691164 Branch:
d16-2 Build date: 2019-07-29 15:54:05-0400
=== Xamarin Designer ===
Version: 16.2.0.379 Hash: 3f0652957 Branch: remotes/origin/d16-2 Build
date: 2019-08-01 17:32:50 UTC
=== Xamarin Inspector ===
Version: 1.4.3 Hash: db27525 Branch: 1.4-release Build date: Mon, 09
Jul 2018 21:20:18 GMT Client compatibility: 1
=== Build Information ===
Release ID: 802030016 Git revision:
f438e4b3ac81dbc614da2f2d9ac3c70ea2e5c350 Build date: 2019-08-09
09:07:01+00 Build branch: release-8.2 Xamarin extensions:
67f026710e882e318fb0c90077b429be3dc0e688
=== Operating System ===
Mac OS X 10.14.5 Darwin 18.6.0 Darwin Kernel Version 18.6.0
Thu Apr 25 23:16:27 PDT 2019
root:xnu-4903.261.4~2/RELEASE_X86_64 x86_64

Answer 1

I opened the project in VS 2017 on Windows 10. I uninstalled Newtonsoft.json, and reinstalled it. Everything seems to work (on Windows). I guess VS for Mac isn't pulling its weight.