"您好,我是否能知道原因呢" translate to "Hello, can I know the reason"
The word 您 as an alternate for 你, implicates that you really respect the person you are talking, thus, you would also need to use 'May I' to show politeness while asking.
I would translate it as follow:
Greetings Sir/Madam, may I know what is the reason?