Solve the problem of WordPress upgrading "The site is experiencing technical difficulties."

Today, when Lao Zuo upgraded the latest version of WordPress to his website, I directly adopted the online upgrade method. After the upgrade, I opened the website and saw the problem of "The site is experiencing technical difficulties.". I panicked a little. Is it caused by incompatibility? In theory, there is nothing serious, but it is just a trouble.

When I saw such a problem, I went to search for a solution. I planned to upgrade again by manual upgrading, but the problem was solved when I opened the website again.

It can be seen that there is nothing to panic about when such problems occur. Because there are processes that need to be recovered slowly during the upgrade process, we should wait a minute if such problems occur after the upgrade. If there are still problems, we should think of other ways.