I can see some errors on your Apache logs like the following one:
Undefined index: super_user in /opt/bitnami/apache2/htdocs/mips/header.php on line 46
It seems that there are some undefined variables in the PHP code. All of the errors seems to be related with
mips. I don't know what is
mips, is that a plugin or something you installed? Is it you own code? In any case, if it is a plugin I would try to disable it. IF it is your code, I would try to fix the errors. You can see the full log under
Regarding the cache, you can start a new private window in your browser, that type of windows don't store the cookies.