Openbox can add named ranges to your models, if you want, by ticking the appropriate option in the “Settings” window.

It tries to add a named range that has the same name you used for the calculation or input. In some cases, that isn’t possible because the name contains characters that aren’t valid in the name of a named range.  Excel Help says:

“The first character of a name must be a letter, an underscore character (_), or a backslash (\).
Remaining characters in the name can be letters, numbers, periods, and underscore characters.

You might want to change the name you use in Openbox and try again.