An eTA can be cancelled in cases where information comes to light that you have become inadmissible to Canada. At that point, an immigration officer would cancel your eTA and let you know by email.
If your application was cancelled, you should not travel to Canada. If you decide to travel to Canada with a cancelled eTA, you will be prevented from boarding your flight to Canada.
We encourage you to reapply for an eTA only once you have addressed the reason(s) leading to the cancellation of your application.