New WordPress Plugin Update Crashed Site

This option is known to create issues just like redirection loops, mixed content, etc.

You should get an SSL certificate and set it on Full (Strict).

If you do not have an SSL certificate for your domain (and www sub-domain and other sub domains if so, excluding the “e-mail”), you could go with Cloudflare Origin CA Certificate.
Here:

A great article about setting up an SSL for your domain at Cloudflare can be read in as a step-by-step instruction on the below article:

Below are some suggestions how to troubleshoot or check the settings regarding the SSL at Cloudflare:

Available and usefull options at Cloudflare dashboard: