Assuming there is nothing with either the lens or the camera body, then yes, your AF-S lens is fully compatible (including autofocus) with the Nikon D3100.

See the 2nd row of the Nikon lens compatibility chart.

If the camera says your lens is not attached, then one of the following is probably happening:

1. The lens isn't fully rotated and latched into position. This would mean the electrical contacts to the lens are not seated or contacting, preventing communication with the camera body.
2. One or more of the lens's electrical contacts are damaged, again, preventing communication between the lens and cameras.
3. One or more of the camera's electrical contacts are damaged. But this would imply likely problems using other modern (electrically-communicating) lenses with your camera. You didn't indicate this, so I'm going to assume it's not the case.
4. A ribbon cable inside the lens is damaged or got disconnected. This isn't common, but it happens, especially if the lens has had a rough life. Luckily, this is easy for a repair center to fix. Some lens models are more prone to this, or have a reputation for this problem to develop. The Nikon AF-S 50mm f/1.8G lens doesn't have a poor reputtion; it's known to be a decent lens for its price, and pretty solidly reliable.

Assuming there is nothing with either the lens or the camera body, then yes, your AF-S lens is fully compatible (including autofocus) with the Nikon D3100.

See the 2nd row of the Nikon lens compatibility chart.

If the camera says your lens is not attached, then one of the following is probably happening:

1. The lens isn't fully rotated and latched into position. This would mean the electrical contacts to the lens are not seated or contacting, preventing communication with the camera body.
2. One or more of the lens's electrical contacts are damaged, again, preventing communication between the lens and cameras.
3. One or more of the camera's electrical contacts are damaged. But this would imply likely problems using other modern (electrically-communicating) lenses with your camera. You didn't indicate this, so I'm going to assume it's not the case.
4. A ribbon cable inside the lens is damaged or got disconnected. This isn't common, but it happens, especially if the lens has had a rough life. Luckily, this is easy for a repair center to fix. Some lens models are more prone to this, or have a reputation for this problem to develop. The Nikon AF-S 50mm f/1.8G lens doesn't have a poor reputation; it's known to be a decent lens for its price, and pretty solidly reliable.

Assuming there is nothing with either the lens or the camera body, then yes, your AF-S lens is fully compatible (including autofocus) with the Nikon D3100.

See the 2nd row of the Nikon lens compatibility chart.

If the camera says your lens is not attached, then one of the following is probably happening:

1. The lens isn't fully rotated and latched into position. This would mean the electrical contacts to the lens are not seated or contacting, preventing communication with the lens.
2. One or more of the lens's electrical contacts are damaged, again, preventing communication between the lens and cameras.
3. One or more of the camera's electrical contacts are damaged. But this would imply likely problems using other modern (electrically-communicating) lenses with your camera. You didn't indicate this, so I'm going to assume it's not the case.
4. A ribbon cable inside the lens is damaged or got disconnected. This isn't common, but it happens, especially if the lens has had a rough life. Luckily, this is easy for a repair center to fix. Some lens models are more prone to this, or have a reputation for this problem to develop. The Nikon AF-S 50mm f/1.8G lens doesn't have a poor reputtion; it's known to be a decent lens for its price, and pretty solidly reliable.

Assuming there is nothing with either the lens or the camera body, then yes, your AF-S lens is fully compatible (including autofocus) with the Nikon D3100.

See the 2nd row of the Nikon lens compatibility chart.

If the camera says your lens is not attached, then one of the following is probably happening:

1. The lens isn't fully rotated and latched into position. This would mean the electrical contacts to the lens are not seated or contacting, preventing communication with the camera body.
2. One or more of the lens's electrical contacts are damaged, again, preventing communication between the lens and cameras.
3. One or more of the camera's electrical contacts are damaged. But this would imply likely problems using other modern (electrically-communicating) lenses with your camera. You didn't indicate this, so I'm going to assume it's not the case.
4. A ribbon cable inside the lens is damaged or got disconnected. This isn't common, but it happens, especially if the lens has had a rough life. Luckily, this is easy for a repair center to fix. Some lens models are more prone to this, or have a reputation for this problem to develop. The Nikon AF-S 50mm f/1.8G lens doesn't have a poor reputtion; it's known to be a decent lens for its price, and pretty solidly reliable.