WP only visible for logged in users / automatic redirect to log in screen

Hello everyone,

I stumbled over a major problem: My WordPress-site which is still under development, but shall be launched end of next week, is not publicly visible.

Alright, so here’s the whole story: I’m using a child theme for OneDesign’s Enlightenment theme and various plugins:

Bootstrap 3 Shortcodes, Coming soon and Maintenance mode WpDevArt, Download Monitor, Email Address Encoder, Google Analytics by Yoast, Google Analytics Opt-Out, HTML Editor Syntax Highlighter, Jetpack by WordPress.com, MailChimp for WordPress Lite, Members, P3 (Plugin Performance Profiler), Page Security & Membership, SVG Support, Team Members und The Events Calendar

Since I’m using a coming soon-plugin, the website is supposed to direct any non-logged in users to a corresponding coming soon-screen. Instead they’re redirected to the log in-screen. So if I’m trying to open https://www.mydomain.com, I’m redirected to https://www.mydomain.com/wp-login.php?redirect_to=http%3A%2F%2Fwww.mydomain.com%2F&reauth=1. Duh!

I tried the following to fix the problem:
1. I checked whether I’ve accidentally activated “Protect the entire site” – I didn’t; the box is unchecked!
2. I disabled a lot of plugins – no success
3. I deleted my .htaccess files – nope
4. I checked the privacy settings of the ‘home’ page – everything seems fine

I honestly have no clue what causes this problem and am more than grateful for any suggestions!