Layout Disappeared

I thought it was a server error, because I had problems during the week with another site hosted on the same account. Anyway, basically I’ve just launched a new site, for a week or more it was fine, but now it looks like this:
https://www.australiamovie.net/index.php

When previously it looked like this:
https://img.photobucket.com/albums/v663/mourou/avatarsNsigs/australiaversion1.jpg

The only thing I can think of is that I had edited the section in the admin panel >> OPTIONS >> general

WordPress address (URI):
Blog address (URI):

I both fields were: https://australiamovie.net/
And I made it- https://www.australiamovie.net/

Would that cause such a problem? I figure it may have changed the path for the css files, but I can’t fix it now.

I can’t access the admin panel to change it back, is there a way I can edit an FTP file to correct the problem?
Is what I did even the source of the problem.