Flow desinger issue with the run as property

[Community Alums]

Hello All,
I have faced the issue in the flow designer: 

When I set "Run as" - System User in the flow property the flow works properly. But when I set "Run as" - User who initiates session then the flow is not working it gives an error while sending the notification step.

Could anyone please explain to me why this happened? 

Thank you.

[Bhavya11]

Hi @Community Alums 

Please bleow URL will be helpful

https://support.servicenow.com/kb?id=kb_article_view&sysparm_article=KB0821206 

Please mark helpful & correct answer if it's really worthy for you.

Thanks,
BK