Some bluetooth devices force others to drop connection from a certain source to get their own private network going. An example is with a bluetooth speaker or car audio.
MESH works with other devices. There are several devices hooked up to one device, most likely a server of some device that allows other bluetooth devices to hook up to them.
Some devices just aren’t compatible with others. Not every device will have the same receive and transfer signal as other devices, which means they will not be able to pair.
Proximity is a key factor in communicating with bluetooth. The device that is trying to be hooked up to a MESH network might be too far away (outside of the allotted area).
Other signals might be interfering with the bluetooth signal such as other radio signals or even Wi-Fi. USB 3.0 actually operates in the same frequency spectrum as bluetooth at a 2.4 ghz so it could possibly disrupt the signal coming from the bluetooth device.