Hi Xènia,
This sounds very much like a plugin or Javascript clash caused by a plugin or theme file that’s not loading a Javascript library as it should.
To test & find out which plugin it is, deactivate all plugins except for Events Manager. Then reactivate each plugin one by one until the problem returns. When that happens, you’ve found the plugin that’s causing the problem.
Hi caimin_nwl,
Suddenly the plugin works perfect, without deactivating any other plugin, by the moment. Thanks for your answer.
Regards,
Xènia