If you enable Moodle debugging (Site administration -> Development -> Debugging), you will probably get an error message displayed in your browser that will help you find out what is wrong.
After the set there was a message :
Fatal error : cannot redeclare mod_hotpot_mod_form ::add_activity_list () in /var/www/elearning/mod/hotpot/mod_form.php on line 594
That line should be at line 495, so I think you do not have the most recent version of the HotPot module.
Please delete the entire "mod/hotpot" folder on your Moodle 2.0 site, and reinstall the HotPot module using the latest version of the zip file:
