I must be missing something, but I set Open Registration to yes and then set the members options page. Hit save. I go back after a save and it says open registration is set.
Then I go to General-> Settings and I get the warning on top that Open Registration is controlled by S2 and it is set to zero.
I go back to the S2 -> general options and sure enough it is set to no.
That is really weird. I just tested what you described, as well as other variations, and it worked right every time.
Maybe it's a conflict with another plugin? You can test disabling the rest of the plugins and try saving the s2Member setting again, see if this time it reflects in the WP general settings page.
It is driving me crazy. I have de-activated all plug in, re downloaded and reactivated a new copy of s2 member but I can't get the open registration setting to remain persistent.
Is there a log somewhere.
I have successfully installed s2 member on one of my sites so I don't think it is user error.
Is the other site that has this setting working correctly, in the same server? I find it very strange that the setting won't save. Do other settings save and stick as they should?
no cache and I have turned off all plugins, unloaded s2member and reloaded with all plugins off, changed themes back and forth to get as clean as possible to no avail.