If it's not a new install, then the file is missing for some other reason because it clearly says "no such file or directory".
Go into SSH and issue this command:
ls -al /usr/local/directadmin/conf
It should contain my.cnf and mysql.conf. If both are missing, something is wrong, then try to access mysql via commandline to see if it works.
If yes, you can create the files manually.
If no, or if it's a new install, you might need to either wait longer or install mysql newly.