Start by nuking your current plan and make sure every workout (especially any you have moved) are deleted. You want a perfectly clean calendar with no dangling workouts.
Then restart plan builder, and specifically set the start data to align with the past date where you did your prior base training start. This leads PB to a better ending by paralleling the actual timing you used and not just starting “today” or part way through your actual plan progression.
You can also test different options via switching the “Experience” setting and I would guess the last two options would give you more emphasis on Build and/or Specialty that are closer to what you may want.
That is the real trick to start. You also want to avoid actually moving workouts and follow a different mindset once you get the plan set, or you will cause future problems for AT. See the link below for best guidance: