Hey there. Any luck with rats since?
I had a problem with these pests too. Though I haven't tested the device you had, but I had something similar like
https://www.amazon.com/dp/B07HC8DJ5R...d_i=B07HC8DJ5R and it was fine. I also checked this
source and various others just to be sure and bought some chemical repellents like
https://www.amazon.com/Exterminators.../dp/B01DTBOV06 and put some on my grill. Worked fine too. Please answer about your case.