Your buyer is willing to pay the invoice, the political situation however is blocking him to pay: the bank transfer to the foreign supplier, is simply not allowed.
Your buyer is blocked to pay despite having enough cash. He’s not allowed to duly pay the supplier due to force majeure.
Causes behind may differ : the country is at war or suffers from political instability; the local government revokes import licences or freezes bank transfers; natural disasters e.g. earthquakes or floods disable the financial traffic, etc.
You, the supplier exporting to foreign buyers, could decide to subscribe an insurance policy covering similar risks.