Hi,
The issue is caused by either the minification engine, or there is indeed an invalid character in one of the original script files. There are two fatal script errors reported in the console, looks like this one completely blocks further execution: https://i.imgur.com/y1aIXBl.png
Errors reported:
If you try to open the drop-down, it does not work either, meaning that the error if fatal, and blocks further script execution.
Unfortunately this has no connection to the plugin, the highlighted code section comes from a different script file. I recommend investigating that section, and correcting the errors there. Once the console does not report any errors, then all the scripts should start working correctly.