Current Microsoft Product team have confirmed that modern commands (buttons created with PowerFX and JavaScript from the PowerApps UI) are not currently visible in offline-first mode. This is a system limitation of the offline-first mode.

At present, there is no supported method for making these buttons visible in offline-first mode.

Any customisations into D365 new buttons are now not being transferred over to this new version of the mobile application. This does currently work in the outdated current version, I am proposing a change to this to allow both new technologies to work together.

Microsoft Advisories:

Expected behavior & Product Group’s Position:

• This behavior is considered as expected for modern commands, as they are still a work in progress.
• The Product Team has stated that there are no current plans to support modern command buttons in offline-first mode or introduce custom visibility rules for them. https://learn.microsoft.com/en-us/power-apps/maker/model-driven-apps/command-designer-limitations#power-fx-and-command-component-libraries-limitations
• The default behavior in offline-first mode simulates the app being offline without an internet connection. As a result, buttons without the "Mscrm.IsEntityAvailableForUserInMocaOffline" rule are hidden.
• While the "force online toggle" was introduced as a possible workaround, it does not resolve this issue in your case.