Failed to install LoRa Server on Raspberry Pi (no dirmngr)


I could not install successfully LoRa server on Raspberry Pi running Raspbian.
An error occurred at step: LoRa Server Debian repository as below figure. Please help me to address this error. Many thanks.

The problem had been solved in few minutes later. I realized that I have not installed dirmngr by command:
sudo apt-get install dirmngr