Serial Number selection under item grayed out

I was recently made aware of an issue we are having with serial numbers. Unfortunately, our old warehouse kid was not entering serial numbers in for products and now we need to start doing so. When I go to the item, the serial number check box is grayed out. How do I fix this?

did u try as Administrator?

I am a System Manager. I do not know if there is an Admin for the hosted version…

That’s kind of strange …have u set maintain stock for the item? …u can have a look at and u can see items with check not grayed