You should get a meeting with your account to negotiate terms for early payment. You could offer a 2.5% to 5% discount for early payment (don't offer too much of a discount up front). If that doesn't work, you should say you will need some up front cash to continue, if their 60 days past due (?) is an undue burden for you.
If it turns out they haven't got any money, it's better to find out immediately so you can cut your losses and move on, or sue.
"The main thing that I learned about conspiracy theory is that conspiracy theorists actually believe in a conspiracy because that is more comforting. The truth of the world is that it is chaotic..." —Alan Moore
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