Problems with SC_dir_app_name

Since yesterday, and especially today, the system has started to give an error that makes the system unusable by affecting the server.
PHP fatal error: Uncaught error: Call to undefined function SC_dir_app_name() in …

Security is enable.

Has this happened to anyone?
I looked in the latest forum and there is a comment but it is from 2012.

Is there any way to fix it manually?

Thanks in advance