Since January 1st all payment attempts made in my website that uses PayPal Buttons haven't completed, because 3DS Redirection is not working.

Once the user has filled the payment form and has pressed the confirmation button, 3DS Redirection seems to start, but after several seconds it leads to an empty window.

Inspecting the window with chrome developer tools I see a HTTP 400 error from PayPal server with the following content:

{
"ack": "contingency",
"contingency": "PAYER_INVALID_FOR_PAYMENT",
"errorData": {
"step_up_context": {

}
},
"meta": {
"calc": "c1f1102886ec5",
"rlog": "rZJvnqaaQhLn%2FnmWT8cSUg9MBfMHgUpSmljgVb0Xwip5zXKuC9mTG091hbpXJKDB4GcbpXWo2fs_176c3f8d7c0"
},
"server": "iAAUzIvOh0KjiUHcIz_zmmVS1DmTy-krLVywz6ZKuwuKCXV66aCq1EkryHpbVCjmC6Kem1VsAGcg7V9PHSf6-j8-foYsgU35kySJu_cgh8ppcNk545aEHdb64FThVQiXcNp-Kb-xW4wKy4B_gZUsWqdT4pU7iI1g6rcWYXnXtWf-CgFz6SVpY9LHr0Con-AFF_QwqTvhfsI0QWAzSQfsZac9l9z3bu57kd2EB-G0h_RgW4a8KJFdVWCpISKTxhOttPfCKw5pGCq"
}

I haven't changed any single line of code in my website.

Thanks