Hi @Narendra90
Pls verify that the Recurrence action is set to run daily:

And also check if you have set the trigger condition to run the flow on 15th of every month. To set up the trigger condition, pls perform the below steps:
Click on ellipses menu (...)

Select "Settings" from sub menu:

Next, add the expression in the trigger condition to run the flow on 15th of every month, this condition will check if current date is 15, if yes then the flow will be triggered it else it wouldn't:

Expression used here:
@equals(dayOfMonth(utcNow()), 15)
If this helps & solves your problem, please remember to give a 👍 and accept my solution as it will help others in the future.
Thanks