Hi @rinu007,
Could you please share a screenshot of your flow's configuration?
Do you add a "Start an approval" action within your flow?
I have made a test on my side, I afraid that there is no way to send the approval email with a table within Details field of "Start an approval" action currently. The current item would be formatted as a HTML text rather than a table within Details field of "Start an approval" action. My flow's configuration as below:
- Add a "When an item is created" trigger.
- Add a Compose action, Inputs field set to Body dynamic content of the trigger.
- Add a "Select" action, From set to following formula:
array(outputs('Compose'))
Within Map entry, the key of first entry set to NameInsuranceCo, the corresponding value set to following formula:
item()?['NameInsuranceCo']
the key of second entry set to CreationDate, the corresponding value set to following formula:
item()?['creationDate']
Note: NameInsuranceCo and creationDate are both columns of my SharePoint list. Using "Select" action to determine which column would display within the table.
- Add a "Create HTML table" action, From set to output of "Select" action.
- Add a "Start an approval" action, Details field set to output of "Create HTML table" action.
Image reference:
The flow works successfully as below:

If you would like this feature to be added in Microsoft Flow, please submit an idea to Flow Ideas Forum:
https://powerusers.microsoft.com/t5/Flow-Ideas/idb-p/FlowIdeas
Best regards,
Kris