What Causes the HTTP 501 Error?
There are a few common reasons why a server can’t meet your browser’s request, causing the HTTP 501 error. Most commonly, the owner of the web server hasn’t enabled a feature needed to complete the request. There’s also the chance that they haven’t installed a required piece of software or plugin for the web server. You may also get a 501 error when the web server is outdated or unmaintained. In rarer cases, the site owner set something up wrong, and the web server software they chose isn’t compatible with a feature on the site.
How to Solve the HTTP 501 Error
Before you start, there is no real way to solve the 501 error as a visitor to a website. The problem isn’t with your computer or web browser. It’s a problem with the web server or the site running on it. The most you can do is reach out to the owner of the site and let them know something’s wrong. If you are the site owner, these steps can help you get to the bottom of the problem causing the HTTP 501 error. For CentOS and RHEL run: On some systems, that’s a little different. Restarting Nginx is similar.
