To toggle between the Unified Client Interface (UCI) and Classic Mode, do the following.
First, open Dynamics 365:

Select Settings->Open in classic mode:

The app will open in Classic Mode:


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hi Carl,
I got a trial version and try to change in the settings but don’t have that option ,
how can i change user permissions in dynamics 365 [that’s what click dimensions support say ]
Hi Danny, it’s possible this feature has been removed. You can try accessing with the url through https://yourorg.crm.dynamics.com/main.aspx?forceClassic=1 (though this may not be reliable) or going through https://home.dynamics.com.
Another way is there Go to Administration > System Settings > General > Use the new Unified Interface only(Recommended) Value to “No”
Hi everyone, about enabling the access for the Classic version, I’ve found this from MS Docs. “In the Power Platform admin center, go to Environments and select an environment. Go to Settings > Product > Behavior and then turn on Show legacy app to everyone, not just admins.”
https://docs.microsoft.com/en-us/power-platform/admin/enable-unified-interface-only