Getting 405 error is a common problem that most of the WordPress users experience. If you find this type of error on your website, you must follow this tutorial to solve your issue. This is not a major issue, but you need to fix this problem as soon as possible.
I have experienced this type of problem on my website when I added SSL to my website. I have another post where I demonstrated how to install SSL on a WordPress website. If you don't know how to install SSL on your website, you must check the tutorial.
How To Fix HTTP 405 Error? WordPress 405 Error on WP Comments Post PHP After Switching HTTP to HTTPS
I made this quick tutorial to help you learning how to fix - http 405 error. Check out the video, hope you will get the solution.