Hello,
today I made the update from 13.0.6 to 13.0.12. Since the Update I can’t view nextcloud via the browser. The client which is installed has the working connection.
Does anybody has an idea what I am doing wrong?
Unfortunately I cannot see any working connections on this screenshots. Log into your server and double-check that the web server is running, that no errors are displayed in the web server log and also the Nextcloud log file.
It is difficult to give more detailed advice without having any information about your server environment, OS etc., etc.
You should also think about upgrading your installation to a supported Nextcloud version, because v13.x is already out of support.