Setting up Remote Desktop Apps for access from a Mac with 2FA

Setting up Remote Desktop Apps for access from a Mac with 2FA.
I have a server 2012 remote access gateway, with remote apps published(which uses single signon), behind a 2FA connection (web based) and want to know if its possible to allow macs to connect to the remote Apps behind it. i cannot permanently remove any
of the above setup as it is a requirement.
When i connect from a mac i can login to both the 2FA and remote access web pages and see all the apps but when i click on any app it downloads it to the mac and when i try to run it using Remote Desktop App for MAC i get an error :
"httpendpointexception: 4, The non-proxy http connection failed to connect with the message: 500 internal Server Error."
I have tried with 2fa turned off for testing and get the same result.Does it support 2012 TSGW server? does it support Remote desktop apps? as i cant find a definitive answer on either.
Thanks in advance for any advice.

Thank you for posting in Windows Server Forum.
From Error description it seems to be a communication issue between your Mac and your RD gateway server. If you connect from extranet, you may need Remote Desktop Gateway or a VPN/Direct Access connection to your intranet, or forward port 3389 on your router.
500 Internal Server Error seems to be a HTTP related error. 
The HTTP status code in IIS 7.0, IIS 7.5, and IIS 8.0
Also, please double check the settings if you have a RD gateway implemented in you intranet.
In Windows Server 2012 R2 RD Gateway pluggable authentication is also introduced. This allows custom authentication routines to be used with RD Gateway. For example building a two-factor solution on top of RD Gateway is now possible which allows doing token-authentication
to the RD Gateway which works seamlessly with RD Web Access or RDP file launching.
Please check below article for more information.
Windows Server 2012 R2 is coming what does this add to RDS – VDI
In addition, please provide the log file from the client for further research.
Microsoft Remote Desktop -> About Microsoft Remote Desktop -> Send log via email
Hope it helps!
Dharmesh Solanki
TechNet Community Support