"The site is experiencing technical difficulties" error is WordPress's usual way of displaying a 500 error. This is specific to your own website rather than a hosting issue.
This is caused by something PHP code related, most commonly caused by a plugin. This could be related to some code going haywire, a bad plugin update, or a plugin suddenly and inadvertently causing a huge spike in memory usage.
As the reasons for this can be pretty varied, and it requires developer-level work to dig into the code to find out the cause, we recommend raising a support ticket so we can investigate and fix the issue as soon as possible for you.
