first check the outgoing email is setup for your SP Farm properly, run the below script to confirm.
Add-PSSnapin Microsoft.SharePoint.PowerShell -ErrorAction SilentlyContinue
#Configuration Parameters
$SiteURL="http://portal.crescent.com/ "
$Email = "salaudeen.rajack@crescent.com"
$Subject = "Test Email from SharePoint"
$Body = "Test Email Body"
#Get the Web
$Web = Get-SPWeb $SiteURL
#Send Email using SPUtility SendEmail method
[Microsoft.SharePoint.Utilities.SPUtility]::SendEmail($Web ,0,0,$Email,$Subject,$Body)
https://www.sharepointdiary.com/2016/09/how-to-test-outgoing-emails-in-sharepoint-using-powershell.html
Thanks & Regards,
sharath aluri