When I try to log on, I get an invalid password error. However, I know the password is correct.
Password is above 30.
By default, the maximum password length is 30 characters. Anything beyond 30 is truncated. The truncated value is then sent to Kerberos/Active Directory (AD), which will fail to match.
Upgrade to Data Loss Prevention Version 15.5
Changes in version 15.5 have increased the limit to 127 characters.