Unable to activate recurring_application_charge by Junaid atique

I am unable to activate users charges. I forgot to activate them on the day when the accepted the charges so Now i am trying to activate them. So here is the story,

The user signup on our app lets say on January 21st with 15 day trial. Here is the charge detail

Array
(
    [activated_on] =>
    [api_client_id] => xxxxx
    [billing_on] =>
    [cancelled_on] =>
    [created_at] => 2015-01-21T03:15:54+00:00
    [id] => xxxxx
    [name] => AppName
    [price] => 9.00
    [return_url] => https://xxxxxxxxxxxx/payment_return/
    [status] => accepted
    [test] =>
    [trial_days] => 15
    [trial_ends_on] =>
    [updated_at] => 2015-01-21T03:15:58+00:00
    [decorated_return_url] => https://xxxxxxxxxxxx/payment_return/?charge_id=xxxxxxxxxxxx
)

Now when I am try to activate the payment, I got 406 error. here is the activation api params.

Array
(
    [recurring_application_charge] => Array
        (
            [activated_on] =>
            [api_client_id] => xxxx
            [billing_on] => 2015-02-12T03:15:54+00:00
            [cancelled_on] =>
            [created_at] => 2015-01-21T03:15:54+00:00
            [id] => xxxx
            [name] => xxxx
            [price] => 9.00
            [return_url] => https://xxxx/payment_return/
            [status] => accepted
            [test] =>
            [trial_days] => 15
            [trial_ends_on] => 2015-02-05T03:15:54+00:00
            [updated_at] => 2015-01-21T03:15:58+00:00
            [decorated_return_url] => https://xxxx/payment_return/?charge_id=xxxx
        )
)

But it always return 406.

Please help.

Regards,