Material & plant &: alternative BOM & not found

What causes this issue?

The system may not be able to find an
<DS:GLOS.alternative_BOM>alternative BOM</> for several reasons.


&sys_admin&
If you have authorization check the following:
RESET N1
In bills of material, check the alternative BOM actually exists.
If the alternative does exist, check the way the alternative is
determined from the cost estimate.
RESET N2
Check that the costing lot size agrees with that of the BOM.
Find out which quantity structure indicator was used in costing.
<DS:TRAN.CKC1>Check costing variant</>
Check which application was assigned to this quantity structure
indicator.
Using this application, check the way the alternative BOM is
determined.

Error message extract from SAP system. Copyright SAP SE.