You usually need to get active that emails are sent (except for invitation emails as user of the backend, for example).
But for the invitation of respondents you need to include their email address in the token table. Most email templates are referring to the use of tokens.
You can also have emails sent to an administrator for each finished response, this would be the long and short administrator email.
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Provide your LS version and where it is installed (own server, uni/employer, SaaS hosting, etc.).
Always provide a LSS file (not LSQ or LSG).
Note: I answer at this forum in my spare time, I'm not a LimeSurvey GmbH employee.