Error 500 after fresh installation of 1.9.12

[fab22]

Hello,

I had the same issue as here for installing : #471
and the trick worked for me too.

But when I click on "launch webcalendar" the site return an error500 on the page login.php.

-I run opera, and had a try on edge too.
-Nothing on the limited server logs I have access from my hosting provider.
-i can see a warning in the console of my browser:

crbug/1173575, non-JS module files deprecated.
(anonymous) @ (index):1788

and I don't know what to search for next, can someone help me please?