I have written an Add-In in C# using the 10.1 SDK. When my client tries to install the Add-In he receives the following error dialog:
I have googled this to pieces to no avail. Solutions for other people seem to be about changing the target ArcMap version in the VS esri config file, but that can't be the issue here. I developed this for ArcMap10.1 and have successfully installed for two separate ArcGIS 10.3 instances (10.3.1.4959 was one, the other I don't know). So I think the target version shouldn't be the issue.
The ArcMap instance that is having trouble is 10.3.0.4322 on a Win 7 SP1 machine.
Anyone have an idea?