Currently you cannot pick up a Queue call using a BLF key on the 3CXPhone app that is ringing on another extension, all other calls though should be OK. I think this currently causes some issues with the call reports.
If you cannot pickup any call using a BLF on the 3CXPhone app, make sure in the Management Console in the Extension Settings of the 3CXPhone extension, in the "Rights" tab that you have the "Perform Operations" checked.