I do not know detailed information about how you implement it. You can follow the normal step to readd the device again and find if it can work.
For gateway, please restart the pktfwd as you stopping it for loiotsudo systemctl enable pktfwdsudo systemctl restart pktfwd2.
For arduino, You have to configure it as below, as you change the Now please open the serial monitor in the upper right corner ( or you can press Ctrl+Shift+M at the same time ).Choose Newline (This option will add “\r\n” at the end of each command.), set the baud rate 9600.
Then tap the commands below and press send.
For EU868 AT+FDEFAULT=RISINGHFAT+DR=EU868
For US915 AT+FDEFAULT=RISINGHF AT+DR=US915HYBRID AT+RXWIN2=923.3,DR83.
3.To test whether you add the device successfully, you can use the serial monitor of Arduino IDE tap the command below. Then you can check the local server website data. at+mode=lwabpAT+CMSGHEX=“0a 0b 0c 0d 0e”