discharge is not automatic - there are 2 hings to do

1. Get confirmation from your lender that you paid your mortgage in full.

Most lenders don't send it automatically - you need to ask for it.
Check what is your lender's formal process for this request.
The lender may have be a discharge fee. This will be in your mortgage contract. Fees range from zero to $400. Some provinces / territories set the maximum fee a lender can charge to discharge a mortgage.

2. Request that the land registry update the title of your property by removing the lender's rights to your property.

Land registries are provincial / territorial agencies and may have different procedures / require various documents from you.
You may be able to arrange with them directly or you'll need a lawyer. Lawyers fees can range from a few hundred to a couple of thousand dollars,

It's important to get this done. You won't be able to sell your home / condo when there is a mortgage charge on it, even you don't owe any money.

There are circumstances when you may decide not to discharge your mortgage. For example, if you were planning to use the home as security for an investment loan - but this only makes sense if the investment loan would be from the same lender as your mortgage.