That is just me, though as I mentioned in a cousin comment it took some time for this to happen. Its not like I've just been working for the last year with out pay. Its more of a natural decay of their ability to pay... so 2.43 years +-
On my second job, my boss once told me not to commit any new code changes to the client's repository until they paid an outstanding bill. They paid very quickly. If they need something from you, use that you get them to pay those outstanding bills.
> their ability to pay
Ability or willingness? Do they pay their own people? Their own executives? That's a choice they're making.
That's the key indicator.. 95% it's willingness.