Why doesn't my iphone 4 sync with my laptop anymore?

I've been downloading music on the laptop and just syncing it with my phone for months now, but suddenly it's stopped working and my phone won't sync. I haven't tried for almost two weeks and today was the first time in a while but for the few weeks before that, I get a pop up everytime I go into google chrome saying that I didn't sign in properly and to check if my account exists. My half brother game my mom a tv show thing for her to watch but it didn't work unless he downloaded this media player thing to the laptop. Could that be the reason? Everytime I plug my phone into the laptop it just keeps vibrating and doesn't even charge, much less sync with the laptop. And when I try to download songs even to the laptop, it just shows up as an audio file and shows the traffic cone looking symbol instead of the itunes logo

Initially I would go to the iTunes website and install the latest version of iTunes, then try to sync again. If no better this link from iTunes support may help
https://support.apple.com/...b/HT204095

Regarding the problem with chrome, you may need to check your Google account details by going to Google and verifying your account details.

Your half brother must have download VLC media player. This wouldn't be the reason for the problem