I am also having the same problem. I have clicked the https button on 'Activate HTTPS' but the page is not showing on membership payment page. I tried downloading and installing the latest version (which I think is already updated v1.6.2) but I get this error...
"Copy failed
JInstaller: :Install: Failed to copy file /my_domain/tmp/install_5391e38220309/com_osmembership/packages/install_5391e3823c4a4/mod_membershipplans/mod_membershipplans.php to /my_domain/modules/mod_membershipplans/mod_membershipplans.php
Package Install: There was an error installing an extension: mod_membershipplans.zip"
So I still do not get a secured subscription page.
This happens on Joomla 3.3.0 because Joomla change their API in version 3.3.0. In your case, it seems thee are some permission issue. So please send us admin and FTP account of your site so that we can install it for you !
