A second player can not join “Better on Bedrock” 1.1.3 by Poggy

My Son purchased “Better on Bedrock” 1.1.3 by Poggy from the markeplace. It says it is intended for 1-8 players. My son is playing on Xbox and I have tried to join on samsung tablet, samsung phone, another xbox and a switch. It loads the resource packs, and then I get the messages below. We have tried more than 10 times, restarting the deivce each time and multiple devices.