The root of the issue may be the use of special characters (for example, a space in your username, password or e-mail address, or something like * % # ! ) which results in an error message. Try creating your username and/or password with only letters or numbers (or both) but no special characters.
Users can then modify username or password information later by clicking their user profile (found by clicking the "head and shoulders" icon on the upper-right side of the screen and clicking into User Profile) and updating.
If you need additional assistance, contact our Support Team at 1-800-323-9084, prompt 1, or firstname.lastname@example.org and we are happy to help.