problem with the editors roles

Hi,
I have installed this plugin on sites of 2 clients, I also installed the User role Editor to make sure the client would be able to work with the plugin.
With the one client: perfect, with the other: problem…
They are able to make newsletters, but not manage the subscribers!

I now had to make them admin instead of editor, which I prefer not to do…
Any idea why it works in the one and not in the other site?

Could it be a conflict with a plugin?
Or is it because the one that works has a premium version of MailPoet installed and the one that doesn’t’t work has a free version of MailPoet?