Error establishing a database connection

Try logging into FTP and making sure there is no .maintenance file, also erase the upgrade folder. Its never a good idea to stop wordpress during an automatic update. Take a look at your wp-config file to make sure everything appears correct, it could of been editing it and you cut it off half way.

WordPress br in content problem

Switch to the HTML editor and you’ll be able to see all of your page markup. You likely have an unclosed tag or extra line return somewhere in the content, so the visual editor adds additional markup to clean that up.

No HTML/Visual mode option in admin panel (New Post)

Turn off all your plugins… then check it. if its all good (what would probably be true) start activating your plugins on at a time to find the problem maker. This happened to me several times and in 9/10 cases was a plugin… the 1/10 time was a nasty code i pasted into my functions.php … Read more