Where is the decline option located?
The decline option can be found in the RSVP block of the form, as seen in the example below.
What is the reason for the decline option not being visible in step 2?
The reason for the decline option not being visible in the second step of the RSVP process usually lies in the fact that the button of this option has been toggled off.
You can resolve this via Setup > Form Builder. You need to enter the settings of the RSVP block (gear icon in the top right-hand corner) and toggle on the button of the 'Can't Make It' option. After that is done, you need to save your changes and republish your event (in case it has already been published).