Same problem here. Solved now. Problem: I cannot update my iphone6s to ios14, and I tried to restart and leave enough space for the update, still not work, so I asked the customer service, they told me this may cuz by the disconnection to Solution: They asked me to connect my iphone to Mac(or PC), in the finder( or iTunes), you can find option "download and update", then you can update the iphone system on the Mac. Remember to keep connection of your iphone to you computer while updating. I believe this can solve your problem too.