Indeed, there is a lot of JavaScript errors on you site, that is the cause of the plugin’s issue. It uses JavaScript to generate the QR Code image on the page and is therefore blocked.
It may be the google maps api error “Uncaught (in promise) Error: Could not load “stats”.”
I tried a fix to the problem, I need you to test it by replacing plugin code through FTP or the WordPress plugin editor (in: plugins > Editor, and select kaya-qr-code-generator).
Can you replace the file ‘plugins\kaya-qr-code-generator\lib\functions.php’ with this content:
https://pastebin.com/hLa3GUa9
When it’s done, tell me if it solve the problem.
Thank you, best regards.