iMac USB port not working

I was trying to connect my iPhone XR to my iMac by using my charging cable to transfer some videos onto iMovie. However, everytime I plug in my phone, my phone alerts me that the phone is being charged over and over again like it was being disconnected and connected (my iphone was responding to the charge being provided from my computer, it just wasn't constant like it is suppose to be). I use this cable to charge my phone every night and this has never happened. I even tried another wire to see if it was a wire issue, but the same thing happened. I also tried an SMC reset and this did not work. Any ideas?