When multiple web adaptors are installed on one machine, then one web adaptor is uninstalled, installing a security patch provided in the following link, http://support.esri.com/en/downloads/patches-servicepacks/view/productid/66/metaid/2110, fails to install and states that the program to upgrade may be missing.
Last Published: October 12, 2015ArcGIS for Server
Bug ID Number
August 28, 2015
July 28, 2020
ArcGIS for Server
Operating System Version
2008 R2 64 Bit
After review by the development team, it has been determined that this issue is related to a known limitation with the software that lies outside of Esri's control. The issue's Additional Information section may contain further explanation.
the base installation must be installed to apply a patch
Reinstall the web adaptor without configuring for the security patch to run.