Before you try a manual install, I'd check if the Path in the system's environment variables is correctly configured for your system.

Given that there's always one shared host that moves forward, it will either pick the x86 or the x64 version on your machine. This issue of not picking the right one might happen if you install multiple/different versions.

Run the where.exe dotnet command to see where the host is looking for the SDK (it's the first entry returned). If you're on a x64 machine, you want to have C:\Program Files\dotnet listed first.

If it's not, edit the Path system's environment variable to have the location you want showing up higher. Doing that should fix the issue of the SDK versions you installed not showing up when you run dotnet --info.

See The latest installed .NET SDK not found for complete instructions.

Answer above by Maira is correct and fixed the issue however for those that need a little help go to start menu, type "path" and select "Edit the System Environment variables". When that opens, under the "Advanced" tab click "Environment Variables". Under System Variables find the "Path" variable and click "Edit". Find "C:\Program Files\dotnet" and click "Move Up" so that it is above the (x86) variable.

I managed to find the answer to this problem, and anyone else who is having this problem can most likely fix it with this solution too! So the reason it breaks is because of the way the .NET Core SDK installer works, it does not install the SDK correctly for some reason, so you have to do it manually. Go to this link, where you would normally get the installer for the SDK but rather than downloading the normal version, download the binaries version. It should download as a .zip, so extract it and then copy the contents of the folder. Go to C:\Program Files (x86)\dotnet\ and then remove it's contents, finally paste your clipboard into the folder. Now try it out, open a new command prompt or PowerShell, and type dotnet --info. It should tell you that you have all the SDK's and Runtimes installed. Keep in mind, you will have to download the newest version of the binaries, that way you have the latest version of the SDK's.

The reason this works is that you are manually pasting the SDK's into the folder, if anyone could start a ticket for the installer to Microsoft, {EDIT: MS created an internal ticket and this answer is wrong. See next answer End Edit} that would be great, and link them to this post so that they can understand what's going on. Some of you might have come here because you are fed up with reading Microsoft documentation and to be honest, so was I! Now this might not fix all the problems you are having, for example, I am still having problems with visual studio and their .NET implementation but if I or anyone figures it out, I will add it to this answer. Hope you have a great day, bye!