Hello @Anne-Marie55,
The "Send special offer" button is available only on reservation inquiries, not on reservation requests.
Reservation-Inquiry-or-Request-What-s-the-Difference?
How do I send a guest a special offer?
You can change t he price of a confirmed reservation by going to yoour reservations, find the one in question and clicking on "Change or cancel" and then on "Change reservation".
Enter the new amount taking note to account for your total nightly rate for the duration of the stay plus any other charges like cleaning fee.
Steve.