Custom code loads then disappears

I own a fashion showroom and want to allow stylist to rent out clothes directly from the website. There’s a rental software company called Booqable, that allows you to use their booking elements on your website with provided codes. I got the shopping cart code to work but the other elements are loading prior to the page loading then disappearing once the page is fully loaded. So annoying. Please let me know if you can help

I would showcase this to Booqable people. Either the code is not being used correctly or something of it is off.