Is there a known error concerning form 760PY, refering to Code 20-amount (TP)? I have tried and failed several times to set the value to 0 since no credit is being claim

I am unable to correct this error.  The box is filled with " 0. ", which I have changed several times.  Every time it loops me back, tells me it still needs to be corrected, and I find that the 0. is back.