Just thought that I would post this here in case anybody else comes across the same problem...

Community Builder: 2.1.3
CBSubs 4.1.0+build.2017.08.03.17.28.44.142dfd725
CBSubs eWay plugin: 4.1.0+build.2017.08.07.20.58.58.bc03b6077

Membership are processed properly if the Offline payment option is selected, but if the eWay payment option is selected you see the following message:

"Gateway Timeout
The gateway did not receive a timely response from the upstream server or application."

The server logs show an entry for /user-profile/saveregisters, indicating that a script timed out before returning headers for index.php.

This install of Joomla is 3.7.4, using PHP 7.1.8 (although I had also tried 7.0.22, and 5.6.31)
I tried disabling other extensions, such as Kuneena, HikaShop, etc, without success.

I thought it might have been a problem with the eWay plugin, so I tried earlier versions of it, without success.

Eventually I tried working backwards through the various versions of CBSubs.

It turns out that on the several SiteGround servers that I have tested this on, the most recent version of CBSubs that will let me process eWay payments is CBSubs 4.1.0+build.2016.09.02.14.13.49.ae734b9bc.
Anything newer than this results in the timeout message.

Hope this helps someone avoid the hassle I experienced trying to sort this out for my clients

Peter

I wondered if it was the outbound HTTP request that was being blocked.
I suspect that it is something that was changed on the server rather than in the CB code, which is why I referred to SiteGround in the subject.
As I couldn't find any other posts about this, I think that it may be only something that affects servers using the same security setup that SiteGround has installed.
Made me pull out a bit more hair, trying to work out what the problem was. I even tried fresh installs of the latest versions of Joomla 2 and 3, with just CB, CBSubs, and the eWay plugin, to see if anything else was interfering