Here is the cause of the problem... as quoted from the website for our development system:
Microsoft refactored their core app runtimes in 2015. They have made what they call a "Universal C Runtime" which has been distributed via Windows Update to all supported versions of Windows that stay up-to-date (which is the default behavior for Windows Update).
Starting with Xojo 2016r1, the Xojo Windows framework has been updated to use the latest Microsoft tools. This allows Xojo to stay up to date and allow the Windows support to be improved in future releases. This means that Xojo now uses the new Univeral Runtime and your built apps now require it.
As the Universal Runtime is distributed automatically via Windows Update and included with Windows 10, Microsoft considers it part of Windows. Because of this Xojo does not include the Universal Runtime DLLs when building Windows apps since most users will not need another copy.
If your users do not have the Universal Runtime, your apps will not run on their systems. The best solution is to make sure the user is up-to-date with Windows Updates. If that is not feasible, then you can also manually supply the Windows Universal Runtime.
What version of Windows are you on?
We might change our installers to include this file to avoid these types of issues...
but meanwhile install the missing file from this Microsoft page: