ERRINVTD008 :Cost Acc No. Is not entered. Please check your GL Mapping in connectwise
ANSWER:
In these cases it usually is the following
1. In the GL account entry. The COGS (cost of goods sold) account is empty.
2. Created the mapping against the wrong product category, or the mappings are correct but created them after he received/closed the purchase so you have to undo the PO status and unreceive and do it again.
Also check out our helpful user guide
also
http://support.innoventsoftware.com.au/solution/articles/222363-mapping-of-gl-accounts