Fatal error on creating first calendar

Hello,

First install on the site, I am getting a fatal error when trying to create my first calendar. On console i get:

TypeError: f.fullCalendar is not a function templates.min.js:1:17890
bookacti_load_template_calendar https://www.monicagiacomin.com/wp-content/plugins/booking-activities/js/templates.min.js?ver=1.8.4:1
success https://www.monicagiacomin.com/wp-content/plugins/booking-activities/js/templates-dialogs.min.js?ver=1.8.4:1
jQuery 4
i
fireWith
x
c

Any help will be appreciated as i bought a couple of addons and would like to actually use the plugin.

I have disabled all plugins, running twenty seventeen theme.
PHP: 5.2.7
MYSQL: 5.6.47
WordPress: 5.4.2

Many thanks,
Hector

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