Form/Calendar select option error ( wordpress plugin, needs a solution)

Hello Freelancers, (problem) The error is the dropdown select option not calling the function getCalender(selectedYear, selectedMonth) on change. (info) I am currently developing a Wordpress plugin that displays a calendar for events. The project uses [login to view URL] for the plugin boiler plate, CMB2 is included as a custom meta boxes plugin. I have attached the zip file, sample posts XML. [login to view URL] = contains actions/filters I have defined a function in the [login to view URL] "function getCalender(year,month)" which returns HTML for the Calendar. If I call the function from the [login to view URL] file, it returns it as on the screenshot. [login to view URL] (line 485) & (line 541) on line (549) if I write echo getCalender($jsYear, $jsMonth); the HTML isnt sent as a response and fails. The problem is probably with the AJAX request not being handled properly or maybe it's possible to do with the CMB2 selection field type, I have been stuck on this for the past 4 days and can't seem to find a solution.