Hi @ArchanaKK
A lot will depend on what actions are used in the Flow...like SendKeys, Focus on foreground window, Image detection, etc.
Adding some logging of your own would help to determine if it stops on a particular line of action.
For Example write some comments to a Text file like...
[DateTime] : Launched Excel
.
.
[DateTime] : Entering For Each loop
.
.
[DateTime] : Excel Closed
When your Flow has stopped, you can go to this text file and see till where your Flow has run.
If "Excel Closed" is missing, then the Flow is failing before that or on that step.
The level of detailed logging and how to handle the growing text file will depend on how you want to write it.
Hope this helps you to track down the error.