Serial Number generation is not working as expected

Summary:

Serial Number generation is not working as expected

Content (required):

Hello Experts,

I want to maintain Serial number uniqueness within a particular Organization.

So, at Inventory Org parameter level, I have defined Uniqueness as "UNIQUE WITHIN ORGANIZATION"

The requirement is such that the items are categorized as Assembly and Sub assembly. Assembly items will have a constant Prefix (ex:111A) and Sub Assembly items will have a different constant prefix (ex:111S).

So, the prefix has been setup at item level. And the Serial Number Generation at Inventory Org Parameter level is "AT ITEM LEVEL".

However, when I try to generate Serial Number for any item, the process goes into "RETRYING" status...