Ian Grieve ran into Problems Logging into Microsoft Dynamics GP as sa After Password Change.
Spoiler alert, it was GP’s 15 character limit for passwords that created the problem. Be sure to check out the whole post.
Problems Logging into Microsoft Dynamics GP as sa After Password Change
Archived post from 2018. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.