MODULE Back in Stock Notification error in email personalization

[fusioneat]

Hallo everyone

I'm using this form to notify product availability. but there's a problem.
when I try to edit the html version of the emails it is not applied to the emails.

I have tried in every way to change the html code of the emails but it doesn't work.here are all the ways I tried to enter my own code:

Back in stock module > email setting > italian > (source code)

 

i also tried to make channges from Intenrational >  Translates > email translation

 

 

any suggestions ?

prestashop 1.7.6.9

www.fusioneat.it