Hi @jonas-hoebenreich,

Thanks for reporting your issue. The fact that the is_ssl() function returns false, means that the detection occurrence if this didn't result in the corresponding fix. Normally, when is_ssl() returns false, Really Simple SSL will detect this, and add the following line to your wp-config.php:

$_SERVER['HTTPS'] = 'on';

You will see that if you do this, is_ssl() will return true, and all redirect issues are fixed.

So the fix in this case should be to investigate why the plugin didn't add this in the first place. The first thing that comes to mind is maybe you had the wp-config.php set to not writable? The plugin should show a notice about it, but on multisite this might be less visible.

Thanks for your reply.
I just checked the permissions and wp-config.php is writable. Since the plugin is causing an infinite redirect loop there is obviously no way to see any notices. For me the main issue was that I did not know what was causing the issue - adding a simple redirect source would have saved quite some debugging time.

Adding the source sounds like a good idea. The notice should appear before SSL is activated within the plugin, so should be visible. I'll run some tests with this: the purpose of the plugin is to make such debugging unnecessary!