Quantity in stockkeeping unit is zero

What causes this issue?

The system has converted the quantity entered in the
<GL:unit_of_entry>unit of entry</> into the quantity in the
<GL:stockkeeping_unit>stockkeeping unit</>. The conversion results in a
quantity that is smaller than 0.001. As only three decimal places are
possible for a quantity, a quantity that is smaller than this (for
example, 0.0003) is interpreted as 0.000.

System Response

A quantity of 0.000 in the stockkeeping unit is not allowed. The system
cannot post the document.

How to fix this error?

Check the quantity in the unit of entry. If necessary, enter the
quantity (not less than 0.001) directly in the stockkeeping unit. To do
this, specify the stockkeeping unit as unit of entry.
If the quantity entered is correct, check the conversion factor defined
in the material master record.
If this is also correct, this means that units of measure that are
unsuitable for inventory management purposes have been defined in the
material master record. Contact your systems administrator.
INCLUDE MB_NA_MM03

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.