Newsletter preview not working

Hi Support,

We use the Avada theme which does not play nice with eNewsletter.
In order to use eNewsletter I normally disable the Fusion Plugin and all works fine.

However, since a recent update I can no longer get the newsletter preview to work at all.
I have tried changing the theme back to the default 2015 version and disabling all plugins, however, I just get a blank page where the preview should be.

I tried re-installing the plugin, but that has not worked either. Any ideas?