E00007 / E_WC_21 User authentication failed

[Simple1Test]

We have been testing with the SandBox for some time now.  All of a sudden (the beginning of Nov) we are now getting: E00007 – User authentication failed due to invalid authentication values.  There have been no code changes on our end.  

I double checked my LoginID and TransactionKey values, they are correct.  I double checked my AuthorizeNet.Environment value and it is SANDBOX.  I know I am calling the test URL, this is the http request header pulled from Fiddler:

POST https://apitest.authorize.net/xml/v1/request.api HTTP/1.1
Content-Type: text/xml
Host: apitest.authorize.net
Content-Length: 898
Expect: 100-continue

Why am am I all of a sudden getting this error?  I have reviewed the blog and found others having similar problems that just magically started working again.

I could use some help with this. I am close to our release date and if I cannot trust the SandBox to be stable how can I trust the Production side to be as well?

[chsriniv9]

Hi @Simple1Test,

This seems to be an intermittent issue . It has been observed that this is solved automatically. Observed that, for few people this issue was solved automatically. Please re-check merchant login Id and transaction key. 

You can check the endpoints and validity of the sandbox credentials using 'Test your Sandbox Credentials' at https://developer.authorize.net/api/reference/#authentication

Also please try to regenerate the transactionkey , sometimes it helps. Please refer the below link for this. https://community.developer.authorize.net/t5/Integration-and-Testing/User-authentication-failed-due-...

HTH, Thanks