I have an instance of Umbraco where I created one document type for each home page of every website with common properties like Name of the Business, Contact Info, Logo. Then I created one document type for each website with the very specific properties.

Everything was ok, but suddenly for all the websites I create, I can add content and I can see it in the Backoffice edit pages, preview pages and I can also see it if I take out the domain and I leave the route just with the route by default, but when I assign a domain to the Home page for the website, Umbraco boot fails saying that A connection string is configured but Umbraco could not connect to the database which is really weird, as all the websites share the same database, they are all in the same instance, and some of the websites work without any issues.

What can I do? Where should I start my search? I have reinstalled Umbraco libraries (maybe something got corrupted I thought) but it didn't make any difference.