I think you are still jumping the gun. I currently have one 2024 client opened (me.) I opened 2024 tax planner, which is for 2025 planning and tried to import my one 2024 client.  It seems to work alright.

I would use windows to remove 2024 tax plan. I would then use 2024 Lacerte for Settings > Update Prepare File to be sure prep file is up to date. Next reinstall 2024 tax plan. 

Maybe just do the update prep file and try again with tax planner.