1.You need to check the public folder for what script is installed on your account, if it is WordPress then check for the index.php script if it is not there then you can add it manually.

Correct ownership and verify the site.

2. The first thing you need to do is to temporarily deactivate all WordPress plugins. This includes any security plugins that you may have installed on your site.

If this resolves your problem, then this means one of the plugins on your website was causing this error.

You can figure out which plugin was causing the error by activating all your plugins one at a time until you reproduce the 403 forbidden error. Then, you will need to delete the problem plugin and look for an alternative.

3.If the other solutions have not fixed the 403 forbidden error on your site, then incorrect file permissions can be the most likely cause.

All files stored on your website have file permissions. These file permissions control who can access the files and folders on your WordPress website.

Incorrect file permissions can cause the 403 forbidden error. They make your web server thinks that you do not have permission to access those files.

You can ask your WordPress hosting provider to check your website for correct file permissions. Some hosts are very supportive, so they won’t mind and will probably fix that for you.