in the assembly item screen, the cost block per item listed comes from the cost block on the item screen – so check the cost block on those items that show zero in the BOM listing

However, that cost shown is a best guess kind of thing for reference only.  Cost […]

Resolution for 'cost block issue: 'Average cost of inventory part is blank while there is average cost, thus BOM cost is not accurate because cost of those items is zero' available: Yes.

The cost block issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the cost block issue yourself by looking for a resolution described in the article. If it is a complex cost block issue or you are unable to solve the issue, you may contact us by clicking here or by using other cost block support options.

For more information about resolving issues related to cost block in Quickbooks/QBO or to get support for the issue 'Average cost of inventory part is blank while there is average cost, thus BOM cost is not accurate because cost of those items is zero', click the link below: