Cannot use Appointements+ with any browser, except IE

Hello to the team.

I installed the plugin but it works only with IE. When I use other browser ( Firefox, Chrome, Safari, Opera ) I cannot click on any date and make an appointment. When I click on any date (green color) nothing happens. With IE everything is fine!

The site is : beepbeep.olamazi.gr/%CF%81%CE%B1%CE%BD%CF%84%CE%B5%CE%B2%CE%BF%CF%8D/

Please can someone check it and tell me any ideas?