Will my probationary period start over even though I've worked here for years?

No, not legitimately, if you're genuinely continuing in the same role through a sale. A probationary period exists to let an employer assess a new employee before extending fuller job security — it makes little sense, and isn't required by law, for someone who has already worked in the business for years to be put back on probation just because ownership changed.

Under the Employment Standards Act, 2000, your employment is treated as continuous, not as a fresh start, when the new owner keeps you on as part of an operating business — your actual years of service are what count, not an artificial restart date chosen by the new owner. If a new owner tries to impose probation on a long-serving employee, that's a red flag worth pushing back on, particularly if it's being used to justify treating you as easier to let go without cause or notice, since your real entitlements are based on your true length of service regardless of the label used.

If you're asked to sign something that describes you as being "on probation" after years of actual service, don't assume the label controls — get the document reviewed before agreeing to terms built on an inaccurate starting point.