Extend range?

So i live in a fairly large house, i have smart things on the first floor, zwaves work perfectly on the first floor, i just installed a few zwave enerwave my guest bedroom down stairs on the right hand side however they don’t work or have a severe delay, how can i fix this, i suspect its a range problem

Thank You

There are two FAQs that should help. ( The topic titles are clickable links)

Start by reading post 11 in the following thread, then go back up to the top and read the whole thread. It will explain about range.

Then read the following FAQ about getting coverage in a large house: