During signature validation, Extension Manager has to connect to server to check CRL, timestamp, etc. It might my be caused by the firewall or the intermittent Internet connection failure. Please click "Tools"->"Preferences" menu item in Extension Manager, uncheck "Allow Extension Manager to access Internet", then install the extension again. This way these checks will be skipped.
follow the instruction but no hope still same silly message
I've the same issue with the same Mac OS 10.9.4 and I've tried many workarounds but no luck
Do you have a specific date to get this issue fixed ?
Please download CC Extensions Signing Toolkit from http://labs.adobe.com/downloads/extensionbuilder3.html . Unzip it to a folder. Launch Terminal from /Applications/Utilities, cd into the unzipped folder, then run the following command:
./ZXPSignCmd -verify <the zxp file path> -certInfo
Please replace <the zxp file path> with the actual extension file path. Check the verification result and paste it here.
Extension Manager CC uses the same code base as the ZXPSignCmd tool.