Xfinity website can't connect to my device and seems not to send a restart signal

When I view my devices on the Xfinity website, it says "we can't connect to your device." When I try to send a restart signal from the website as it suggests I should do, the process takes pretty much the full twelve minutes that the website suggests it will (as indicated by the blue bar), but the lights on my modem never go out and I lose internet connectivity for a few seconds at most at the start of the process and have internet connectivity for the remainder of the time. Furthermore, when the process is done, the website still says "we can't connect to your device."

Why is this? I am attempting to restart the modem because we are having landline voice quality issues. The wifi is working fine.