What could cause a sin input to turn into a square wave across a non-inverting amplifier?
You potentially have a gain of 480 so it is likely that your output is being limited by the power rails of the op-amp. This makes it look like a square wave.

Another problem is your mid-rail generator - you are using 1Mohm resistors and then R4 (100 ohms) connects to this midpoint - this is not going to work well at all. With such a small value resistor as R4 you need a much "stronger" mid-rail generator.

What you could do temporarily is connect R4 to your most negative supply rail via an electrolytic capacitor and re-check your circuit functionality.

Putting a capacitor in series (maybe 100uF) restricts gain at frequencies below 16 Hz but allows you to proceed and debug any other issues that arise. If you do need a gain of up to 480 at DC then you will likely have to use a different mid-rail generator circuit built around a second op-amp.

I'm also noticing that you are not using capacitor decouplers on the rails of the op-amp - these are nearly always required on any op-amp.



EDIT - maybe you have a x10 probe on the output and you don't realize this!!!