Adding https Subsite

Hello there,

I want to change one of my subsites from http to https.

My main domain is already https and now I activated a Lets Encrypt SSL certificate etc.

I removed the http version of the website in domain mapping. relogged in with the network adress and added the domain with https. But every time I add the adress and submit it, its saved as http and not as https.

When I log in to the network area and go to domain mapping, it is added as https. But on the subsite itself it is listed as http.

When I set up the Domain to force https – I get a too many redirects error.

I tried following:

1. change to with better search and replace plugin

2. I deactivated all plugins except domain mapping

3. I removed all redirects form htaccess file

4. I changed the siteurl and homeurl in /wp-admin/options.php to

But nothing helped… Do you know where the problem could be?