That error does not indicate that it is unable to detect it - it's detecting it just fine.
It's not uploading to it. Unfortunately the sync error is extremely hard to debug over the internet, because it is so incredibly non-specific, and the people who encounter it are frequently working with their first or only arduino board, so everything needs explanation. It could mean anything from the wrong board selected, to the board having been cut in half - and anything in between. I used to say, at least it means that your drivers are okay, but then I told a few people that, and then someone else told them to reinstall the drivers, and they said it worked - so you can't even conclude that much! (I still have NO CLUE how that error could possible come up if the drivers weren't okay, as then there would be no serial port to select, let alone get an unexpected response from) That's when I just stopped trying to help people with it.
The Arduino community very dearly needs some way to help people who have this extremely common type of error; I attempted to create such a guide, but after around an hour of work, I looked around and realized I was deep in the weeds, and decided to go work on something I could be successful at - I have no shortage of projects that involve my getting cash moneys for work with microcontrollers. Even when I've gotten this error myself, it has sometimes come and gone with no apparent change in conditions.
Of course, to you, this post is probably worse than useless....