Hi, Erel, Thanks for replying. If I am using the same code as B4J, I also check Kmatle in the thread. I notice that if the target device has no mobile data or internet, the sent messages are then received when it is connected, This is not the case when the deviceis turned off. So I thought of the function delay_while_idle = true, which I read in the Firebase documentation, by default it is set to False, this would cause the notifications to be sent only when the device is online, solving the problem, I do not know if I am wrong . Regarding the Id, put a global variable to assign a different id to each notification, and that worked well, is it the right way? regards