Can't confirm replacement rental modem

I keep getting notified via email and on my Xfinity account that my rented modem needs to be replaced and upgraded. But every time I go to confirm, I get the error "Looks like something went wrong. Please refresh the page and try again". I've been refreshing, trying again, and trying different browsers on different days to no avail. I also responded to a text inquiry about this to confirm that I did indeed want to proceed with the replacement- but that was weeks ago and I have heard nothing since. How can I successfully get my rented modem replaced as requested?