Does Anyone else have Rejection Code R0000-500-01 and has TWO middle names and only ONE last name? Yet no matter the combination you use, you still get rejected?

Use the name that is on the current Social Security card.

The IRS matches the last 4 digits of your Social Security Number to the first four letters of your last name, based on what is on record at the Social Security office.

It is possible the SS office thinks your second middle name is the start of your last name.