H&M 8909ST Stafford armrest detached

I have a H&M Stafford Executive Chair 8909ST. The armrest seems to be getting detached from the back of the chair. I have attached a picture.

There doesn't seem to be any dowels or nails in this joint. I can slide a piece of paper through the gap in the wood!

Is there any way I could fix it?

Attachment 10192

I would take that to an upholster near you, any good shop can repair that. If close to Hickory, NC, you could take it to the Hancock & Moore factory for repair.

Thank you