Running the same app on multiple Quest headsets using the same Meta account can result in a known bug/issue where the headsets will show a warning “Already playing this game on a different headset” or "multiple devices can’t be on this app at the same time"
This is a known issue related to "App sharing" that Meta introduced when adding multiple account logins to their OS. This prevents any app from running at the same time when "App sharing" is enabled on any of your devices.
You can read more from other users experiencing this at: https://communityforums.atmeta.com/t5/Get-Help/Resolved-Issue-App-Sharing-Not-Able-to-Play-Simultaneously/td-p/953691/page/65
We've been working around this issue by removing guest accounts and disabling the app-sharing feature on Quest headsets that are all logged in to the same account. This allows Arkio and other apps to run at the same time on all your devices simultaneously. An alternative is having multiple Meta accounts to manage these headsets.
If you have more Questions about this. It's best to contact Meta customer support as they should be able to help and offer alternative solutions when available.