I can not log in to Apex Data Loader. When I enter my credentials they do not work, and the message I get is "Error logging in to Salesforce. Please check your username and password".
What I have done:
checked multiple times that I can log in directly to Salesforce.com with my username and password.
have someone else on a different environment download Apex, and use their credentials to log in, it also did not work. They can log on to Salesforce.com but not to Apex Data Loader.
We're using a non-profit license for Salesforce.com, if that makes any difference.