No, you would be unable to claim the First Time Home Buyers Amount in 2019 or 2020. You must claim this amount in the same year which you purchase the home.
What you'll need to do now is make an adjustment to your 2018 tax return, as well as your spouse's if the claim is being split. You can make the adjust online in your CRA My Account if you are signed up for one, or mail in a paper adjustment form to your tax centre. Be sure you have some sort of documentation to back up your claim as CRA quite often requests it when adjusting for this tax credit.
