it sounds like you may have Javascript error that breaks the system and stop it from functioning normally.

Look in your browser's console (in Chrome and Firefox you can click F12 and then look for the "console" tab) if you see any error messages when you try to add a block

Thank you for your response. There is a JS error when trying to add a block. I attached an image of the error. Do you know how I can resolve this?
Thank you in advance!

if you activated pretty URL make sure you added the proper bit of code, provided by C5, to your htaccess file.

And also, if you disabled pretty URLs, make sure you removed that bit of code from your htaccess.

Also look for anything that might be doing a redirect of any kind in your htaccess file

Hello,
This is what shows in the pretty url display box when accessed from systems & settings:

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME}/index.html !-f
RewriteCond %{REQUEST_FILENAME}/index.php !-f
RewriteRule . index.php [L]
</IfModule>

ok so if you checked the box to enable pretty URL, make sure that code is present in your htaccess file.

You can only have one of 2 situations for things to work:

The checkbox is checked, enabling pretty URLs AND that code is in your htaccess file

OR

the checkbox is unchecked and you should NOT have that code in your htaccess file.

Just to be sure you know what I am talking about, the htaccess file is a file at the root of your website named .htaccess

If you discover you don't have that file at all but the pretty URLs checkbox is checked, then uncheck it.

Ok, thank you. I did not find an htaccess file at the root of the site, so I unchecked pretty urls. I restarted the server, and still get the same 500 internal server error:

http://localhost/.../index.php/tools/required/edit_area_popup.php?c... 500 (Internal Server Error)
send @ jquery.js?v=9e0bd46b972237b450874b30ad3350d8:4
ajax @ jquery.js?v=9e0bd46b972237b450874b30ad3350d8:4
jQuery.fn.dialog.open @ ccm.app.js?v=9e0bd46b972237b450874b30ad3350d8:3
(anonymous) @ ccm.app.js?v=9e0bd46b972237b450874b30ad3350d8:3
dispatch @ jquery.js?v=9e0bd46b972237b450874b30ad3350d8:3
i @ jquery.js?v=9e0bd46b972237b450874b30ad3350d8:3

well given that error you have, something somewhere is interfering with that operation but it could be anything and because your website is hosted locally and not live, there isn't much else I can say about it.

Something you can try is to go to the file referenced in the error message and use a log at different points in the file to try and find out where it fails

Thank you - I ended up resolving this. I appreciate all of your help :)

You're welcome.

Could you post your solution? It might come in handy to others finding themselves in the same situation.