Symptoms

After disabling SSL and all "older" TSL versions. (Before TLS 1.2) After doing this, AppDeployment is not able to verify the URL specified and AppDeployment cannot be completed. 

Diagnoses

SSL and early TLS were given as examples of "safe encryption" until October 2014, when certain vulnerabilities were discovered, including (but not limited to) exposure to padding attacks that effectively decrypted sensitive cardholder information. All merchants must be PCI compliant by end of June 2016. 

Here is an article that explains the problem.
https://www.pcicomplianceguide.org/pci-ssc-data-security-standard-3-1-guidelines/ 

Resolution 

A coldfix was provided with an updated AppDelpoyment.exe file that we applied to the environment and that solved the problem. If you run into this issue, please log a support ticket and request the fix.