Hi @kylep,
For you "Recurrence: Runs once a week at 19:00" and "We want to search the last 24 hours from 19:00",could you explain more about how frequency would your flow run?Does the flow would run every week or every day?
If the flow would run every week,please choose on which day the flow would run and set the trigger as below:

If the flow would run every day,please set the trigger as below:

In addition,if you would like to check if there are email arrives from the last 24 hours from19:00,and the email is send by "sender@outside.com", the email's subject is "servername", and if the email exists,you would send the email,you could take a try to create a flow as below:


The expression in the Conditionas below:
@and(and(equals(items('Apply_to_each')?['From'], 'sender@outside.com'),equals(items('Apply_to_each')['Subject'], 'servername')),greater(items('Apply_to_each')?['DateTimeReceived'], addHours(utcNow(), -24)))
If there are email arrives from the last 24 hours from19:00,and the email is send by "sender@outside.com", the email's subject is "servername", and if the email exists, the result of condition2 would be true,and the flow would run successfully as below:

Please take a try and let me know if your issue are solved.
Regards,
Alice Zhang