Problem in IR2112 use
As configured, this device is intended to drive a half-bridge with an upper and lower MOSFET.

The bootstrap cap, C2 + C1, requires an active pull down device to charge it.  A passive resistor load of 1K will not allow the cap to charge in time to supply gate drive to the top load at any reasonable frequency.  Neither will it allow you to turn the top FET on and leave it on.

The bootstrap cap charges when the top FET turns off, in your case through the 1K load resistor.  33uF and 1K is about 33mS to charge to 63%, but the time you have to charge is 25us with a 20kHz square wave drive.

Even with just 100nF the time constant with 1K is 100us.

33uF is a very large value for a bootstrap cap as well, they are typically more on the order of 100nF, so not sure why you have the extra cap in parallel.

Your 1K Vgs resistor could be changed to 10K or more, 1K seems small.