@Chrysta29 In the past, special functions like resolution requests have often been unusable in the mobile app. I don't know if this has been corrected recently, but if the guest is genuinely unable to access this function, my first suggestion would be to switch to the Desktop version of the website (which also loads on a phone browser, though it looks terrible).
Anyway, what your guest asked of you was effectively a 1-day extension of the booking, unless you happened to have an incoming guest arriving later at night. Another way to put that through is a booking alteration to push back the checkout to the next day and charge the additional night, at the rate of your choice. That function also works better on the desktop version, though.