500 http Error

I installed and configured suiteCRM about two months ago. It was running ok. I created leads, oportunities, task…

But today, when I started using it, I keep getting 500 internal error. It happens when I’m editting or creating a new instance of any object (when creating or editing tasks, contacts, lead…)

I re-runned chmod 755 of the installation guide.
I also runned the chown apache:apache but I received operation not permitted.

I’m running the 7.8.19 version.