I'm a developer of an ArcMap Add-In and I sign the Add-In with a valid certificate with the ESRISignAddIn.exe tool:
C:\Program Files (x86)\Common Files\ArcGIS\bin\ESRISignAddIn.exe
In ArcMap 10.0, 10.1 and 10.2, The Add-In manager show that the Digital Signature is Authenticated, see next picture:
If I open the Add-In Manager in ArcMap 10.3, the same signed Add-in is invalid but that is not true.
What is here the problem? (see next picture)