ConnectWise PSA has 4 different product types:
However, in Sage, there are only 2 different product types (with regard to accounting):
ConnectWise PSA Inventory items, i.e. #1, are mapped to Sage Inventory items, while the remaining 3 ConnectWise PSA item types, i.e. Non-Inventory, Service, and Other Charge, are mapped to Sage Service items.
Sage Inventory items require a COGS account on the Linked tab
Sage Service items require an Expense account on the Linked tab
While COGS is still considered an expense as far as Sage reporting, it is the Account Class that matters.
The classification of COGS versus Expense account classes in Sage is on the Class Options tab of the account