Lost all the fields in the edit section

Hi,
I just found this plugin which I really find great!
I installed the plugin.
It works fine. I even copy the javascript from Medium for the height problem 1000px.
It works perfectly but suddenly after changing the code in one of my newsletter.
All the fields disappered. I can not anymore change anything like display comments or not in the edit.
I also try to delete and reinstall the plugin but nothing change.
I have lost all the fields. I can just have the short code in the text and the preview but nothing more.

I don’t know if this plugin is still follow (no new issu last 12 months) or not because the page https://mailchimp-campaigns-manager.com seems not to be active anymore. I wanted to susbscribe too.

Thanks for your help.
Isabelle