Q:

Why am I receiving an ' Unable to retrieve card details from iATS. Error: Invalid Username or Password' Error?

I'm using the following steps to produce this error:

Under the 'Contributions' tab of a contact on CiviCRM, click 'Recurring Contributions'

Click 'View' under the individual's recurring contribution

Clicking any of the following links (View, Edit, or Process)...

...results in the following error: 'Warning: Unable to retrieve card details from iATS. Error: Invalid Username or Password' (please see screenshot below)

Donations seem to be processing fine on CiviCRM and iATS, and CiviCRM and iATS seem to be communicating fine with each other (other than this error). 

A:

Two thoughts: 
1) you have an iATS admin agent code 01 (and possibly more: 02, 03) and iATS agent codes 80, 81 and up for payment processing. Is it possible that the payment processor agent code/passwd that this particular contribution is linked to did have a password edit?
2) does your passwd for the agent code linked to that particular recurring series perhaps have any non-alphanumeric characters in it? Those are not recommended as we have seen them work in some cases but fail in others.

