If you have encountered an error when making changes to your Ninja Forms, there might be a few tweaks that you need to do in your server.
Some users experience getting this message when trying to save new changes: “406 Not Acceptable. An error on the server caused your form not to publish. Please contact Ninja Forms Support with your PHP Error Logs.“. Don’t worry, this is easy to fix and often is just caused by some security feature in your server.
To fix this
1.) Log in to your host’s Cpanel and look for “ModSecurity” at the Security section and click it.
2.) Disable your ModSecurity for the mean time. Once that’s done, try editing and saving your Ninja Form again.
3.) Don’t forget to enable the ModSecurity again after those changes to add back your server’s protection.