Hi chrisrein,
Welcome to Centrify!
From the description, it looks like something is blocking from BIG-IP in establishing the connection. You may need to check with BIG-IP to see what is blocking behind. In doing some research online, someone is seeing similar as well:
https://devcentral.f5.com/questions/session-cannot-be-established
Please let us know if there is anything we could assist with.
Kind Regards,
Albert