Error in SendRichMail Process

Hi All, 
We have below error while sending mail to Manger to notify that the user is created.
ErrorMessages = (2019-10-23 09:56:51.200) Executed on: server_default
[810298] Parameter 'Requestor' not found.
When checked for the process parameter, we could not find any attribute like ‘Requestor’.

The Manager account is Active with a valid email address.
Could you please assist in this concern as we have many FROZEN jobs with this error message. 
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