Do I have to tell the new owner about my medical accommodation all over again?

Not from scratch, but a short conversation is still a good idea. When your employment continues with a new owner, the accommodation you already have in place doesn't just evaporate — it's part of the existing terms of your job, and a new employer stepping into an ongoing employment relationship should honour accommodations that were already properly established, not treat you as a brand-new hire with no history.

That said, the new owner is entitled to understand what the accommodation actually involves in order to keep providing it properly — modified duties, schedule adjustments, equipment, or whatever your situation requires — especially if the details weren't fully documented or transferred cleanly from the old employer's records. It's reasonable for them to ask you, or with your consent your old employer or doctor, to confirm what's in place, rather than starting the entire process over as if nothing existed before.

If a new manager seems unaware of your accommodation or is pushing back on continuing it, put the existing arrangement in writing yourself and reference how long it's been in place, rather than assuming you have no choice but to justify it all over again from zero.