Dashboard error (HTTP 500 Internal Server Error)

Clicking on WP Cerber in the admin dashboard left sidebar shows “There has been a critical error on this website. Please check your site admin email inbox for instructions.”

I can still access the Traffic Inspector and can see a “HTTP 500 Internal Server Error”

PostSMTP plugin has been disabled with no effect. The site cannot (and does not need to) send emails, so no admin email.

WP, theme (storefront) and all plugins are up to date.