Keep getting 403 while save setting

Usually, the issue you encountered is caused by a security feature that your hosting provider has set up on your server, which prevents the plugin from saving its settings properly.

So, to resolve this issue, I suggest you to contact you hosting support and ask them the following: they should check if your host has any mod_security settings that forbids sending of URLs/content as POST parameters, or any other rule, that could forbid this to happen. If they find such a rule, ask them to remove it. Also, you could describe the issue you are having to them, maybe they know how to fix it. To describe your issue, you can tell them the following:

“When I submit any kind of content in a custom form using POST method, in a WordPress plugin I am using, I get a 403 page forbidden error on submission. Please disable mod_security on my server because I suspect that it is preventing the plugin I use from functioning.”

After they will remove this restriction on your server, the plugin will be able to save settings.

Let me know if this info helped.