During periods of change, some level of resistance is a given, and not all of it is bad. Often, your staff’s pushback can help identify deficiencies in the new workflow. Addressing such feedback can help you win “converts” to the new process. They can become allies who help you gain the support of other team members with lingering reservations about the changes.
No matter how well you respond to feedback, a percentage of staff will be dead set against changes on general principle. You will not win them over with explanations, training, chocolate, or anything else. The goal of a well-run change management process is to minimize the adamant opposition.
You may need to consider other assignments for such an employee: for example, maintaining legacy documentation in the old system, particularly if that employee has extensive domain knowledge. You must weigh the value that this employee provides to the organization against the drag introduced by general recalcitrance and its effect on other team members.