Unable to see buttons Decline or Accept on Event page layout

Hi all,

According to the following thread:

https://salesforce.stackexchange.com/questions/244058/accept-event-and-decline-event-buttons-not-present-in-lightning-experience

we should be able to see the buttons Decline and Accept when switching to Classic. The buttons are per standard on the page layout, but even in Classic I can not see them.

Do I need a permission to be able to see them in Classic?.

@Salesforce Administrators & Developers, @Data Quality & Management