Working with a customer and also conducting some testing in my lab I discovered that with Horizon 7 Instant Clones I wasn’t able to RDP into them. I verified my firewall settings and also that the ‘Allow connections from computers’ piece was enabled. After various tests I discovered once installing the Horizon 7 Agent it disables TLS 1.1 and 1.2. I resolved this issue by installing a patch from Microsoft on my VDI image to add RDS support for TLS 1.1 and TLS 1.2 (Microsoft KB3080079). Additionally, my endpoint needed the RDP 8.0 update (Microsoft KB2592687) to also enable TLS 1.2. Once putting these two pieces in place I was able to RDP into my Instant Clones with no issues.
KB Reference links to support for TLS 1.1 and TLS 1.2
VDI Desktop: https://support.microsoft.com/en-us/kb/3080079