Hi @ stumac_31,
Could you please share a screenshot of the configuration of your flow?
Could you please share more details about the error that you meet when the flow run fails?
If you want to send an email to one or more recipients using Office 365 outlook, separate multiple email addresses using semicolon would be useful , as is said in the first link that you provide,
However, if you want to send a PushNotification to Powerapps with multiple email addresses, I'm afraid it is not suppported in Microsoft flow currently, as is said in the second link,under Microsoft Flow, it would double quote the input string, which makes it only one parameter for the recipients.
With only one Email address entered, the PowerApps push notification would work as expected.
If you would like to send a PushNotification to Powerapps with multiple email addresses, you could submit an idea to Flow Ideas Forum:
https://powerusers.microsoft.com/t5/Flow-Ideas/idb-p/FlowIdeas
Regards,
Alice Zhang