Resolve 403 Error on WordPress

My WordPress site has suddenly started throwing a 403 error and is now inaccessible. I’m unsure whether it’s tied to a recent plugin, theme change, permission issue, or something at the server level, so I need a specialist who can quickly diagnose the root cause and get the site back online... (Budget: $10 - $30 USD, Jobs: cPanel, CSS, HTML, JavaScript, jQuery, PHP, Web Development, Web Hosting, Website Design, WordPress)