A call system/center failure could certainly be in progress, but looking at weather.gov, with tornado watches across IL, IN and MI, amongst other weather issues, like wind advisories across much of the NE, in the mixer, it's entirely possible that delays are simply a function of volume, as cancels/rebooks/modifications are predominantly done with humans and, if many travelers are like myself, they're on the phone to a call center whilst standing in line at an airport hit with IRROPs.