When I try to open VS2017 from the editor, I get the pop message “Could not open Visual Studio 2017 for project D:/build/IS/Game/InnerSanctum.sln”. I have switch my editor preferences to use Visual Studio 2017 vs just Visual Studio
DId You solve it? I have the same issue
Despite lack of specifics provided in the OP, from your other posts I am assuming that you are working with installed source build of the editor (as opposed to build from the launcher). I have experienced the same issue with UE 4.19.2 and VS2017.
Fear no more, it has already been fixed for 4.20 release, with commit 3e72773.
Following up on the last reply by sensvos, the linked commit leads to a 404: Unavailable page. 
That said, running on a fresh install of 4.20 from the launcher, I have just also encountered this issue. I can manually open the solution, but launching from the editor gives this exact error and no further information.
I’m running:
- Visual Studio 2017 Community
- Windows 10 Pro (x64)
The only weird thing is that I have VS partially installed on a secondary drive (since it won’t let you do a full external install), and UE4 is also installed on that secondary drive.
Based on Mike’s initial report, that sounds like one possible common factor.
To have access to the UE4 source code and avoid 404 you need to connect your Epic Games account with GitHub as described here. However, as I mentioned before, that fix does not concern launcher build of the engine.
Moreover I just tried accessing VS 2017 Enterprise from launcher version of UE 4.20 on Win10 x64 Pro and I cannot reproduce this issue, it is working as it is supposed to. If you think it is of any use for you, I have both VS and UE installed in the default directories on the system drive.
Still and issue with 4.21 though.
I installed VS through UE4 project creation dialog into default installation folder.