Error: Too many redirects on WP Multisite

Hi, I have a wordpress multisite setup which works fine. I created my first site on this platform today and the proces went good. BUT when I want to login to the admin panel of the newly launched site, I'm getting a Too Many Redirects loop. When I want to visit the site I just get a blank screen.

Don't know if it's useful info, but this setup runs on a subdomain. I also have a second subdomain (different db) where I run a multisite network. On the other subdomain I don't have this redirect issue.

What I have done so far:
- Checked my redirects in .htaccess
- Deactivated all plugins

So far nothing helped. Hope you guys might have a solution.