Error after latest update

With the latest update (today?), my WordPress site went down and only says, “There has been a critical error on this website.”

I suspected a plugin update, so I went in FTP and disabled any plugins that were recently updated. The site worked again, so I enabled them one-by-one. When I got to Send In Blue, the problem came back.

I really want to use this plugin – how can I identify the root problem? Or can you do another update to resolve this issue? Thank you.