I'm having issues with that joiplay gives me an error even on the windows version
In the JOIPlay app, open up the menu with the button in the top right corner, then go to settings. Once there, open up "HTML Settings", and see if "Allow External Modules" is on. When I turn that option on, I get the exact same error you are reporting, so if it's on for you try turning it off. (Ensure you click the save button in the bottom right after changing the setting or it will revert on you.) If that doesn't work also check the NWJSAPI setting and ensure that is on. If neither helps let me know and I can see if there's any other potential solution.