A family of Microsoft relational database management systems designed for ease of use.
So, what you are doing is re-creating an accdb from the template? We don't often hear the term "switching" applied to doing that. We usually call that "instantiating an accdb" from the template.
I was able to instantiate the accdb from the old inventory template, so I think it must be okay itself. From the look of it, it must have been an Access accdb from 2007; at least that is the look of the design to me.
Can you instantiate the Northwind Developer Edition Template? It was created last year and has a much more useful inventory design, if I say so myself.