I'm getting the E00001 error in sandbox today. I checked my soap request and it looks correct. This is what it looks like (x replaced with the actual information):

<soap:Body xmlns:soap="http://www.w3.org/2003/05/soap-envelope"> <GetCustomerPaymentProfile xmlns="https://api.authorize.net/soap/v1/"> <merchantAuthentication> <name>xxxxxxxxxxxxx</name> <transactionKey>xxxxxxxx</transactionKey> </merchantAuthentication> <customerProfileId>xxxxxxxxxxxxxxx</customerProfileId> <customerPaymentProfileId>xxxxxxxxxxxxxxx</customerPaymentProfileId> </GetCustomerPaymentProfile></soap:Body>

I know that soap is being depricated and am in the process of switching to use the recommended way but I'm trying to figure out why this isn't working right now.