Issue with multiple 11p-b thermometers

Hi all

I have bought two of the the above wireless thermometers. The first one linked with the app no issues at all but the second one cannot be detected. Even more irritating is it doesn’t matter which one I open it will connect with the app but not both. Did I miss something somewhere it says you cannot have two?
Many thanks

Is it possible to make a screen recording of the problem and email it to