Select (check) the option for assigning serial numbers automatically in
Document Types when issuing goods (see autoassign
serial numbers). Select this option for issues from
Goods module as well as issues from customs
warehouse.
In contrast to on-the-fly manual selection of serial numbers (see
example in assigning unique serial number or
example in assigning batch serial number) the
corresponding number of serial numbers are automatically removed from stock
after you have entered the quantity issued.
If stock is insufficient, issuing serial numbers automatically is not
successful and the following error is returned:

Close the window clicking
.
Solution:
1. Check the entered quantity in issue - It may be higher than the
actual quantity issued.
2. Check if the correct warehouse is entered - Perhaps the item is on stock
in some other warehouse.