API Suddenly Not Working

API Suddenly Not Working

Getting the classic code 4500 ( Problem occurred while processing the request) suddenly today on any API request we make.  We are not over our limit.  Our auth tokens are all good.  We are otherwise communicating fine with Zoho CRM, just can't use the API to sync our records.  This is obviously a huge problem for our sales force.  

Anyone else having issues?  Anyone have a clue on troubleshooting?  No response from support ticket submitted.  :(