Filtering a Square Wave into a Sine Wave
You need a bipolar amp with a bipolar signal, the bottom half is cut off because the negative power terminal of the amp is connected to ground. The amplifier can't create a voltage lower than the negative power terminal. 

Either shift the signal up to half of (or within) the range of the amplifier, or create a negative rail.

You need grounds in the simulation, or the node voltage cannot be determined by the simulator (just like you can't solve the voltage on paper without the ground either).