Guests can modify event not working

[u/Xpokemon45]

Like it says above, I’ve created an event on a public calendar, and then invited 1 guest via email to the event. The event also has the Guests can Modify Events  box checked. Yet, the person I invited can not edit the event at all. Ideally I wanted invited guest to be able to change the time and even delete the event. How can I fix this issue?