@dfrombe,
Thanks for the link. I used it and was able to resolve the issue. I already had the server key created and just needed it copied into the API key location on the plugin.
I must have an old version of the plug-in, because the links to the support are no longer good. The product has changed hands and now seems to be called WR-PageBuilder by WooRockets (formally IG-PageBuilder by InnoGears). Perhaps the latest plug-in won’t have that same affect. I will try switching over to it when I have time. For now it causes issues on few of my pages when I deactivate it. I’ll have to wean my site off it.
I was having this same issue and when I deactivated IG-PageBuilder, the MailPoet menu appeared in it’s place.