This is the test your code fails:

test.assert_equals(check_coupon('a12v564', 'a12v564', 'March 5, 1998', 'March 25, 1998'), True)

Please, fix your code. Storing the day in a single digit/char is wrong.

I doubt that, your day_expiration contains only a single digit.

You should debug your own code, but it's a problem with how you parse your expiration date. Add some prints, see why it fails.

Your code is failing the previous test, the log appears above the test result. Not a kata issue.

Mersi frumos fratelo! ;*