@Alicia753 I have tried accepting the booking request on both app and 2 different web browsers. I've uninstalled and reinstalled the app. I've cleared history and cookies on desktop.
Airbnb support did have me ask the guest to retract the booking request and then request again, which the guest did.
The only thing I had changed just prior to this issue was the availability setting. I changed it from 1 day advanced notice to same day in order to fill an unbooked weekend. I've made this change many times in the past, without issue, so not sure if that is what caused it.
Thanks for your quick response!