I have two thousand water controllers use Class C with abp mode in large scale factory building.Let me describe how it work.When the Users use app to open it,Loraserver will send a downlink frame to node,node will work for it and then node send a uplink to server.You know the nCoV-2019 in China,so these nodes are freeze about 2 months,But I forget to set the device-session time,all session is timeout,these nodes seems like no addr and two keys in activation pages,I use API Interfaces to set it again,but all these nodes need to send uplink then them can send downlink.But If these devices are re enabled, they will be powered on at the same time due to the internal wiring of the building, and some of their uplink data will be lost, which will result in the loss of uplink data. This part of the devices cannot be worked because they cannot be downlink.So Brocaar Can you help me with this questions.Thanks