Invalid IPN error

A recurring payment was just processed. Funds were transferred and received, but we received an invalid IPN error notice (test below).

I can't figure out why this happened and your help would be appreciated. The onl change we have made is to go live and move the site from /newsite2 to the root directory.

I'd very much appreciate your help in debugging this as we are expecting new subscribers shortly!

Many thanks,
Andrew

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Error Log Details-
Message: Invalid IPN
Record Id: 44
Record Type: PayplansPayment
option: com_payplans
gateway: paypal
view: payment
task: notify
mc_gross: 14.00
invoice: 8O56WJCMAUGK
protection_eligibility: Eligible
address_status: confirmed
payer_id: CAZ6SU7CFNNGU
address_street: 8100 Evergreen Lane
payment_date: 07:38:38 Oct 22, 2018 PDT
payment_status: Completed
charset: windows-1252
address_zip: 98040
first_name: Lara
mc_fee: 0.71
address_country_code: US
address_name: Lara Sanderson
notify_version: 3.9
subscr_id: I-H88DPN4H54TW
payer_status: unverified
business: hannah@creatrix.gallery
address_country: United States
address_city: Mercer Island
verify_sign: A3CJtXeWX4g58J.4uEzwviQFZbkpAswJbgMhQfevqJ4m2Ps5Sa2l5pWv
payer_email: lara@sanderson.org
txn_id: 7N874395N5013631P
payment_type: instant
last_name: Sanderson
address_state: WA
receiver_email: hannah@creatrix.gallery
payment_fee: 0.71
receiver_id: 8UHDBFZMNN6VU
txn_type: subscr_payment
item_name: Creatrix Membership (Self Posting)
mc_currency: USD
item_number: 8O56WJCMAKDK
residence_country: US
transaction_subject: Creatrix Membership (Self Posting)
payment_gross: 14.00
ipn_track_id: 456ec66ad31f6
Itemid: 101
id: 0
payment_key: 8O56WJCMAUGK