WordPress Landing Page Troubleshooting

Need help troubleshooting a WordPress landing page where changes are not saving properly. The page is already built, and the issue appears to be related to permissions or settings preventing updates. Whenever I try to make a change and hit the Publish button, it gives an error: Server Error (500 Error). Looking for someone who can diagnose the problem, identify the cause, and implement a fix so changes can be saved and published without issues. Please share relevant experience with WordPress troubleshooting and page updates.