We had a very large prickly pear paddle out near the street. People would break off a paddle or a branch of paddles and merely stick them in soil and root them. I would suggest hydration prior to this event, if the soil is dry, in the sense that it is a repotting. Also an appropriate mix, which may be leading the problem you are having now with possible root rot.
They really hold water a long time even though the soil is dry, but people will water the soil when it is dry, thus changing the nature of the root environment from a wet/dry/wet/dry cycle which the plant understands to a continously damp one. This effects transpiration, which is about all the fat little fellow has going for it to slowly draw nutrients and so forth up inside. It also promotes vagabond fungi in the soil.
@zigs and some others know much more than I about house bound cacti though. Perhaps they can correct me or embellish some pertinent ideas that will be of help.