Kamala did quite well in the election, it was close. In hindsight I don't think there was any particular evidence the polls were inaccurate. Poll-watchers like fivethirtyeight.com predicted that the election was a coin toss (with the toss sliiightly biased towards Trump up until their final forecasts from what I recall) but whoever won the coin toss would probably achieve a comfortable victory. That is pretty much what transpired.
If you want me to refer to private polling you're going to need to hint which poll you mean. I'm working off public data which was pretty accurate on aggregate, there weren't any surprises on election night which was something of a https://www.xkcd.com/1131/ moment.
I dunno. Given the public polls seemed to be accurate in hindsight that just suggests Harris' internal polling was off. They were the C-team that were losing to Trump with Biden and struggling to match his raw charisma with Harris' campaigning. Maybe their pollster wasn't very good or they didn't do that much polling? We can't really assess what was going on inside the campaign in that way.
