Hi @pacodub ,
Did you trying to send the email if Order Status is Changed to "Completed" using this flow. If yes, you can use this approach as well. I created the flow in my environment please review it and give it a try at your end.
I created two SharePoint Lists with following Columns:
Customers:
- Name (Single Line of Text) [I renamed the default "Title" Column as "Name"]
- Email (Single Line of Text)
I added one test record.

Orders:
- Customer (Lookup column to Customers list, Name)
- Total Price (Single Line of Text)
- Status (Choice: Created, In Progress, Completed)
I added a test record and set the Status as "In Progress" initially.

// Power Automate Flow
Now here are the details about the POWER AUTOMATE FLOW:

Please adjust and configure the content of the mail accordingly.
//Testing
To test the flow, I changed the Status to "Completed".

The Flow triggers and sends the email to the customer's email address.
//Output in email:

//NOTE:
The above flow sends an email on each modification of an item in the 'Order' List irrespective of the status field. To prevent this, please make sure to add the trigger condition.
To add trigger Condition:
Click on three dots(...) of the trigger > Setting > Trigger Conditions > Add trigger Condition (given below)> Done.
@equals(triggerOutputs()?['body/Status/Value'],'Completed')


Now, the flow will only trigger if "Status" Column is modified with value "Completed".
Please try it and let me know if you have any questions or if you encounter any errors.
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Thank you,
Harsh Deol