Who builds software like that!!!!
OK. The answer is obvious. Microsoft. As a developer the amount of time wasted due to Microsoft's woeful decisions is huge.
After some testing I found a solution that may work for the client that gets around the problem for them. I'll make my notes available in the MyAnswers section of my site for clients. This doesn't solve the problem. Only Microsoft can do that by releasing Microsoft Access 2016 runtime with a Click To Run installer.
Until Microsoft solves this problem I'd highly suggest that you consider sticking with the version of Microsoft you currently have and I wouldn't hold your breath waiting for a solution.
I'm still shaking my head. Why would a company like Microsoft even consider releasing software they know can't be installed at the same time on the one computer?
The joys of software development. Makes life interesting and challenging.
Kelvin Eldridge
www.OnlineConnections.com.au