How do I pay my federal taxes if the IRS hasn't processed my return ?

Hello, I filed my taxes (state and federal) on 1/26/22. I received my refund for state already and I chose  the "pay later" option for federal because I owed. I wanted to start making payments because the April deadline is approaching and I don't want to be fined. However, my federal return says "still being  processed" and when using the payment tool on the IRS site it says "balance unavailable at this time". I've also had NO LUCK trying to call the IRS every morning in March. Its now April 5th, what do I do?