I am copying the reply from the support thread you opened in case anyone encounters the same problem. If you have additional questions or comments, please post them in the support thread.
Using custom plugins in the device simulator isn't a supported option and that is why you get the error there. You can see more information about the simulator limitations here. As for mobile devices, without seeing your project, it is hard to determine the cause of the issue. Confirm that you are using the OAuth.io plugin from the verified plugins marketplace:
There are detailed instructions about the plugin usage in this page and a link to a sample app.