What Marco describes is very common with the UV-5R series of radios and the 2-pin Kenwood "style" programming cable. Sometimes the shell of the plug needs to be trimmed to allow the plug to fully seat in the socket. Sometimes it requires some wiggling of the plug and a firm push to get the plug fully seated. I've never been in possession of a UV-3R, and don't follow any UV-3R groups, so I don't know if the UV-3R even has this issue. I assume that both of your UV-3R radios use the 2-pin plug. Or are they both the single pin version?
Another possibility is that Baofeng (or should I say Pofung) changed the "string" (aka "ident") that triggers the cloning process. They did this for the UV-5R about a year ago when they introduced the BFB291 firmware. This same thing just happened recently with the UV-6.
Unfortunately, if this is what happened, CHIRP can't be updated until the new "ident" is known. This is don't by "sniffing" the serial communications between the OEM software and the radio during a download. So until/unless you can find OEM software that works with the radio, there is nothing CHIRPwise that can be done.