Renew warranty

The 1 year warranty, cannot be extended once expired.

If you purchased Apple Care+ for it originally and it expired, it can be extended indefinitely with the monthly version within 30 days of expiry: link-> Extend your AppleCare+ coverage - Apple Support

VikingOSX wrote:

No. Once your 12-month warranty has expired, and if you purchased AppleCare+, it too would be done after three-years of the first AppleCare purchase. You cannot purchase AppleCare now.

Did you happen to read the first paragraph of the page I linked?

• If you paid upfront for an AppleCare+ plan for your Mac, you might be able to purchase new coverage that renews annually.

Purchase the new coverage within 30 days after your original coverage ends. To find out if you can purchase the new coverage, go to mysupport.apple.com and follow the onscreen instructions. The new coverage automatically renews until canceled."

Probably not.

See: Extend your AppleCare+ coverage - Apple Support

No. Once your 12-month warranty has expired, and if you purchased AppleCare+, it too would be done after three-years of the first AppleCare purchase. You cannot purchase AppleCare now.

Two minutes between our posts and I was likely still typing… Yes, I read that bit about the AppleCare+ subscription before I posted but the OP did not provide background info either.