Invalid shipping method (SHIPMTHD)

Hello Guys, 

I need help with the a couple of errors I am getting recently when integrating into GP using eConnect. 

Error with POPTransactions

Sql procedure error codes returned:

Error Number = 989  Stored Procedure taPoLine  Error Description = Invalid shipping method (SHIPMTHD) - it does not exist in the Ship Method Master Table - SY03000

Node Identifier Parameters: taPoLine                                           

Error with SOPTransactions

Sql procedure error codes returned:

Error Number = 927  Stored Procedure taSopLineIvcInsert  Error Description = Shipping Method does not exist

Node Identifier Parameters: taSopLineIvcInsert                                 

Weird part about these errors are, these started out of the blue. 

Can someone help me in understanding these errors ?

Thanks,