Venmo works on mobile so when you click the link on your phone or scan the code with a phone that has Venmo app, it redirects inside the app.
They now support a web version and since then the plugin supports it as well as you can see on our store at gurastores.com/test
Once you update and use your venmo username (without the @) instead of the venmo id, you should be fine like it is on our store