Hi @daniel.anez,
Regarding permissions: How should file permissions be set? - #2 by ctgraham
Described symptoms may occur if cache isn’t renewed after theme change.
If it’s not a cause of the problem, you can test OJS on your local machine. I’d make a copy of the site, database and files folder and installed it locally. If it’s reproducible, the next step is debugging locally, if not - the problem is probably in the server environment.