Invalid use of null or Invalid procedure error when posting a transaction to Quickbooks

The most common cause of this error message is when an item exists in All Orders which was never created in Quickbooks and the item has not been assigned a proxy and is not in the sync queue waiting to be posted to Quickbooks. To resolve this issue follow these steps:

-Open All Orders as the admin.

-Go to the file menu, maintain, advanced tab, run db command, and paste in the following script:

insert into SyncQ (UniqueID,TxnTypeID)
select NCItemInventoryID,100 from ItemInventory where ListID is null and SyncQB=1 and Proxy is null

-This will add entries to the sync queue telling the system to create the missing items in Quickbooks. Perform a sync to create the items in Quickbooks.

-Try and post the transaction to Quickbooks again.