The same for me! I get this error all day:
Sorry, we were unable to send this message. We take this very seriously and are working to fix it. Please try again in a bit or report this problem to customer support.
We apologize for the issues you are experiencing with messaging candidates, we are currently experiencing an issue that is causing this which the team is aware of and is working to resolve as soon as possible.
Could you please clear your cache and cookies or log in with another browser to check if you`re still experiencing the same issue?
Let us know if the issue persists.