Payment processing declines have increased dramatically - what could be happening?

[4noggins]

My webstore has seen a dramatic uptick in orders being declined.  Customers are getting a message at checkout that there was an "error" when placing the order.   PayPal says that these transactions are being declined by the credit card issuer.  In my order management system they are shown as "Processing".  Even my attempts to use the Virtual Terminal are not working and perfectly valid credit accounts are being rejected.   I am losing a lot of business and PayPal (despite operating 24/7) choses to not have personnel who can help for 1/3 of the week.  

  I dont know what to do!  Can anyone help

[AtomicV]

I hope you had some luck and things turned out because I'm in the 2nd week of it now, have 2nd tech ticket sitting not even looked at business support have 3 times over shrugged their shoulders more or less. Have gone through every setting I could possibly find & am now just thinking it might be easier just to close account and start again. But still unsure??