Symptoms or Error
Users unable to launch the published desktop from the Mozilla Firefox.
Getting error messages :
Error 1
The connection to “PA-Desktop” failed with status (Unknown client error 0)
Error 2
Unable to launch your application. Contact your help desk with the following information: Cannot connect to the Citrix XenApp Server. The Citrix SSL server you have selected is not accepting connections.

Solution
Solution 1
Download the x64 bit Mozilla Firefox:
Working Firefox version – 53.067 64bit
Non-working Firefox version – 52.0.2 32bit
Solution 2
Recommend to test the workaround provided in private fix LC9388 – Add the following string to the SSL Cipher Suite Order GPO of VDA:
TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384_P384,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384_P256,TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384_P384,TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384_P256,TLS_RSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_AES_128_GCM_SHA256,TLS_RSA_WITH_AES_256_CBC_SHA256,TLS_RSA_WITH_AES_256_CBC_SHA,TLS_RSA_WITH_AES_128_CBC_SHA,TLS_RSA_WITH_RC4_128_SHA,TLS_RSA_WITH_3DES_EDE_CBC_SHA
或者使用Chrome浏览器