Hello @Liz461,
the option to send a special offer is available only when the guest sends a reservation inquiry. It's not available for reservation requests. Guests send a reservation inquiry when they're not yet ready to commit to making a reservation as they wish to ask some questions so sending a special offer may prompt them to book. When a guest sends a reservation request they've made the decision to book at the advertised rrate so Airbnb doesn't offer the special offer option.
You can ask the guest to withdraw the request and send a reservation inquiry. They send an inquiry by clicking the "Contact host" link on the listing page. You should temporarily turn off instant book if you decide to do this, turning it back on when the guest accepts the offer.
Alternatively you could message the guest telling them that you'll refund a certain amount if they book.
Difference between a Reservation “Inquiry” or “Req... - Airbnb Community
https://www.airbnb.com/help/article/35/how-do-i-send-a-guest-a-special-offer
Steve.