If you are having a problem with saving the Theme Options, you have a Server Error 500, Server Error 404, Server Error 403, or you're addressing an empty page, here's a list of possible causes we've been collecting over time. As you can see the problems are always related to host resources that interrupt saving of the options. Please understand that Uncode is super-tested and trusted product. If something, as important as the Theme Options, does not work (and only in your installation), the problem is to be evaluated in some server-side settings.
Firstly, we encourage to ask your host support why using one of top-seller themes of ThemeForest produce an error on this server and ask to verify the specific error information they can read in the Error Log file.
If you save Theme Options and you have an error please verify that you don't have any red messages inside your System Status related to Memory Limit. The WP Memory Limit is the maximum amount of memory (RAM) that your site can use at one time. You generally have a Memory Limit issue when your installations is not compliant with the Server Requirements for a modern WordPress installation.
If you save Theme Options and you have an error please try to deactivate all your extra plugins to check if this fix the issue. For example a few users had performance issues with extra plugins.
If you save Theme Options and you have an error this can be related to an out of date version of PHP, please verify that your host is offering you the latest and official suggested by WordPress that is PHP 7.
Some few hosts limit your resources. When you save Theme Options you compile some actions at the same time and they not permit you do this. Please ask them to review these settings for you.
This is the reply from a collaboratiove host:" Yep, you're triggering some of our security triggers known as Mod Security. Looks like the delete call generates a bunch of backend calls at a single time that is freaking out the system. We've gone ahead and disabled this rule since this is only triggered from an admin area it shouldn't increase any exploit risks for your account."
Pattern match (ModSecurity)
An user reported the problem was a pattern match blocked by the host:
Request: POST /wp-admin/options.php Action Description: Access denied with code 403 (phase 2). Justification: Pattern match "(?i)([\s\"'`;\/0-9\=\x0B\x09\x0C\x3B\x2C\x28\x3B]+on\w+[\s\x0B\x09\x0C\x3B\x2C\x28\x3B]*?=)" at ARGS:_uncode_post_custom_fields_settings_array.
The easy solution is to go to: Cpanel ---> modsecurity --> Deactivate.