3 days ago my phone would connect to my computer perfectly fine, but now it isn't working. At first I thought it was the usb cable, but after purchasing a new cable it still doesn't work. It isn't my computer because my dads samsung connects to my computer. I noticed usb tethering is off and greyed out. Is that the issue? If not, what is?
Depending on your computer os and your phone. After connection via usb, theres normally a popup in the notification bar where you are able to choose from various usb modes. If that won't work, it could be a driver issue. Samsung devices tend to have Samsung Kies installed, which ships the usb driver.
It could be just the cable. I have seen situations where one cable will pass data and another one won't, even if it had done so in the past.
So try another cable and see if the problem persists.
First, unlock your phone. Now go to the notification bar and click on the notification that has appeared there. Select file transfer (MTP). The phone will reconnect to the computer using file transfer mode. If this doesn't work, try getting the latest phone drivers for your computer.