(solved) error 500 fast cgi fcgid MaxRequestLen

Under apache2 and php 7.2 using mod_fcgid when you click “Save changes” you get error 500
No explanation in Browser Console F12

You must look at your php error.log under the vhost where error happened

If you have:
mod_fcgid: HTTP request length 131484 (so far) exceeds MaxRequestLen (131072)
(*131484* can be different in your case)

easy solve is:
1. increase a bit upload_max_filesize in your php.ini
upload_max_filesize = 2M (2M its default value, simply increase it to a higher value. Normally 4M will be enough. Keep in mind this value controls the max file size a user can upload in your server / website, so if plugin doesn’t restrict it, and you use a very high value here, your users will be able to upload bigger files to your server / website)

2. increase a bit FcgidMaxRequestLen in your apache2.conf file. You can do it in your main apache2.conf file, or in each vhost you have. Normally you won’t find any line with FcgidMaxRequestLen, so you simply add it anywhere in the .conf file

FcgidMaxRequestLen 131072 (131072 its default value, simply increase it till you can “Save changes”)

Important note:
Before making changes to your php.ini and apache.conf files, make a backup of them, just in case you make things worse.
In order to Apply changes you make in php.ini and apache.conf files, you MUST RESTART apache2. You will have to login again in your wordpress site.