It's funny how this happens. I have spent the whole night trying to figure it out. But I couldn't.
In the Settings => General Configuration, when I try to turn Site On/Off, it works fine. But when you put in code, any kind of code, then I get the error message.
In Site Promotion => Analytics, same thing happens. I can't put in the tracking code because it gives me the above error message. But when I put in normal text, it works.
I haven't tried the same with Settings => Terms & Privacy but I have normal text there so there has been no problem.
My Site Settings
PHP 7.2.3 and all other requirements fulfilled.
.htaccess in root folder created by the software in Overview => Security
Cache type is MySQL + APC as set in Settings = Advanced Configuration => Data Storage
All security requirements fulfilled as in Overview => Security
I have tried to be as detailed as possible. Sorry if I've come a little short.
My conclusion is that it won't accept code.
But my question is why? What could be the problem and how do I fix it? I'm I the only one who has come across this?
Thanks in advance folks!