.XLAM Is Already Opened

I'm having some trouble with a custom add-in that I wrote. Everything works fine but every time I open Excel it alerts me that *.xlam is already open. and then it prompts me if I want to re-open. I'm writing this add-in for a corporate client and obviously cant have this error popping up every time excel opens.

Currently the file is saved in Users\*Me\AppData\Roaming\Microsoft\Addin ... which I believe is the normal default for when you save an .xlam Addin file.

Additionally, the Add-in checkbox is checked under Options > Add-ins Available

I've tried uninstalling the add-in and repeating the process but the error keeps happening - any help would be greatly appreciated!