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