Hi @Annie ,
Check as following:
①Please add the action "Log to history list" to check if the workflow runs successfully.
If the email has been sent, the message we logged will show in the description.
②Make sure you have configured outgoing email at farm level(Central Administration> System settings> Configure outgoing email) and the web application level(Central Administration> Manage web applications>select the web application> General settings>Outgoing E-mail ), and the related exchange server works well.
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③We could also check the workflow status page to find if there are any error messages, like this:
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