My power is out, an AT&T technician is coming over tomorrow morning to install an internet 50 upgrade, and I cannot reschedule

The power in my area is currently out and supposedly won't be back up until 6PM tomorrow, so I tried rescheduling the appointment through AT&T's website but this bizarre glitch keeps occurring where as soon as you load up the page where you reschedule the appointment, the little section where you're supposed to select the new date/time just disappears as soon as the page loads:

(the red arrow is where the little section would briefly appear)

I tried different web browsers, deleting cookies/cache, even tried using different devices entirely yet this weird glitch keeps preventing me from making an appointment change. I also tried changing it through the myAt&T app but the error "Something went wrong on our end. Try again a little later" keeps appearing.

Since AT&T will just not let me change my install appointment, at this point I'm just hoping that the technician will have some sort of workaround for installing the internet 50 upgrade despite my power being down. Will the technician actually need my power to be on for the installation? Will they have a power generator in the event that power isn't available? Just not sure what else to do at this point.