On my WordPress dashboard, I am unable to see the ADD NEW plugin button.
The Plugin menu when over PLUGINS is not here also.
define('DISALLOW_FILE_MODS',true);
I try to add
define('DISALLOW_FILE_MODS',false);
but it does not work.
Can someone have an idea about this issue and how to fix it?
Try reinstalling WordPress. Possibly your wp core files effected from one of your plugins. Reinstalling WordPress may help,