Can't query Zuora

[jmlilly]

My production system stopped working.

I am making API SOAP calls.  C#.NET.

I seem to be connecting just fine.

It is failing when making the first call to query payments. I'm passing a query string like this: 
SELECT AccountId, AccountingCode, Amount ... 
FROM Payment 
WHERE PaymentNumber > '" + pmtNo + "'" 
AND Status = 'Processed'

I'm throwing an error on this: 
return zs.Query(sql);

Could not establish secure channel for SSL/TLS with authority 'www.zuora.com'

This started failing on Monday this week