Site doesn't work well

I have an account with the site, https://www.thecalendarcreator.com . It is a software that creates calendars for the present and future years. I have turned off Enhanced Tracking for the site (that worked for another site of theirs that I joined). Some functions work, many do not work correctly, if at all.

My computer is a Mac, v 10.13.6, so it's getting old. I have contacted thecalendarcreator.com support, and they can't find anything wrong on their end. They have suggested that perhaps it's some sort of anti-virus setting on my end. I've been looking at my Settings, but I'm no techie, so I don't know what to do. I would greatly appreciate your help, so I can hopefully get this site to work.

Thank you very much, Lea Lashaway