When you check the console, you might see error on jQuery and that could be few things is happening. But the immediate resolution as below:

• Check if you have turned on Rocket Loader on Cloudflare
• Exclude jQuery from defer

/jquery-?[0-9.](.*)(.min|.slim|.slim.min)?.js
/jquery-migrate(.min)?.js

Read more : https://docs.wp-rocket.me/article/1496-how-to-fix-the-jquery-is-not-defined-error