Button Worldwide Operates under Net 45 policy, but refused to pay after 60 days Boca Raton, Florida

An agreement between my company and Button Worldwide stipulated a payment schedule of 25% on contract signing, 50% on software delivery, and 25% on final approval.  To date, I have received only the initial 25% payment.  Software was delivered on 28 Aug (almost 60 days ago).

One week after delivery, I sent an email describing a software defect I discovered and requesting a meeting to coordinate release of a software update, but I received no reply.  Two weeks after delivery, I received an email from Button demanding that I immediately fix a defect they had encountered, which turned out to be the same defect I had attempted to resolve in the previous week.  I made several attempts to coordinate with their staff to deliver the update, but each time a meeting was scheduled, their staff did not show up.  As of this writing, they have not rescheduled the meeting, and they have not provided any notice or confirmation of final approval.

When I had not received payment by the 45 day mark, I sent an invoice describing in detail the outstanding payment.  I received a response from them in the form of a revised purchase order, which described the outstanding balance as roughly $500 less than my invoice amount.  I politely asked them to reissue this purchase order with the correct amount, but I have received no response and no payment to date.