When using a registered domain for a nopCommerce store, a SSL certificate will need to be installed on the site before SSL can be enabled. An overview for installing a certificate can be found in the following article:
To enable SSL, log into the store and then enter the Administration section of the site.
Then the SSL setting can be found within Configuration > Stores > Edit
Make sure to update the "Store URL" with "https", check the "SSL enabled" box and then "Save".
If only SSL is enabled without also updating the Store URL, it will lead to redirection loops when visiting the store.
In those cases, or if SSL has been accidentally enabled without a certificate being installed, the setting can be disabled by following the instructions here
. If you are unfamiliar with performing updates directly to the database, a ticket can be opened with Support