I agree the ISP needs to answer why I am receiving an "AUTH-NAK msg request denied" not "Access Reject" and I am not running side by side sessions but am testing one at a time. There is definitely something that the ISP does not like which is coming from the SRX but I need to find out what that is.
Unfortunetly, I am having a huge headache trying to pry that information from them since it is the Australian NBN and they are the wholesaler to my ISP. I am battling to receive the information and will keep on trying.
In the meantime, I'll be trying the upgrade very soon and will get back to you on the results.
Cheers.