IATS plugin 1.5.3 in Civi 4.7.11 on Joomla 3.6.2

First off, CiviContribute works like a charm.

Second, in backend (test) and frontend (live), CiviEvent form comes up and goes to second step correctly. Upon submitting for payment times out with this error but the payment is processed as per IATS TEST88 portal:

On Chrome:
> **This site can’t be reached**
>
> The webpage at
> https://alcoholjustice.org/administrator/?option=com_civicrm&task=civicrm/event/register
> might be temporarily down or it may have moved permanently to a new
> web address. 
> 
>ERR_SPDY_PROTOCOL_ERROR

On Firefox:

> **Request Timeout**
> 
> This request takes too long to process, it is timed out by the server.
> If it should not be timed out, please contact administrator of this
> web site to increase 'Connection Timeout'.

I'm not getting any log reports even with debugging on. I increased the PHP input and execution time limits to 5 minutes. It times out at 2 minutes.

Also, just want to be sure this is the correct URL for iATS:
https://www.iatspayments.com/netgate/ProcessLinkv2.asmx?WSDL