Im Not Able To Save Changes

When I make change using page designer I'm not able to save the change.

Screen just rolling without changes as per image attached..

Can you pin point reason why this could happen. We never had the issue before..

and we using sytist from 2015

Most likely is triggering mod security on the server when saving and stopping the process.  Mod security is good but also has false positives. 

You would need to contact your hosting company support and let them know you are triggering it and they can whitelist the rule you are triggering. 

Thank You for pointing us in the right direction, we will contact them to follow this up !

Here is what we have received from our hosting company it may help other users:

"Unfortunately, it seems like your site has hit some of our ModSecurity rule, ModSecurity is a server-side application firewall that we use to stop hackers from maliciously trying to compromise your website, this includes common compromises to outdated applications, cross script injection and much more.

Generally, when a rule is hit it may be due to a false positive or in most cases lines in the code that are programmed sloppy.

I have excluded the specific rule ID "300076" that your account has hit to ensure that you're not blocked again, if for any reason you hit a different rule on the server please let me know and we can exclude that as well. We highly recommend that users use the latest versions of any software applications installed"

FYI,  it is because HTML code is being posted to save to the database. And some content in that code is what is triggering mod security.