Exchange2016 iApp would not create the AAA pool for APM

Hello everyone,

 

I am building Exchange 2016 infrastructure and using Exchange2016 iApp V2 running on LTM 12.1.2 HF1.I can easily create the iApp without APM authentication but when chose to use APM and put the AD information it throws below error. the AD is a new node on the LTM and hasn't been used anywhere else (cause I know that might create a problem) also all the communication is open on the fire wall side ( I could even join the NTLM machine to the domain) but the iApp wouldn't take the AD info ( i even tried a dummy IP and still the same). Any thoughts?