If it is sealed from AMD in a Official AMD Retail box it should have a Warranty on it. Normally new AMD Retail Box Warranty is for 3 years.
I do know if you purchased a AMD processor and it was RMAed and AMD replaced it, the rest of the 3 year Warranty is still in effect for the replaced processor.
To tell you the truth I have never seen a Refurbished AMD Sealed Retail box processor being sold.
I would open a AMD SUPPORT Ticket under Warranty and ask them from here: https://www.amd.com/en/support/contact-email-form
I'm not aware of any refurbished products having a full warranty. Usually 90 days. Although I may be wrong with the CPU's. Although I've not had any problems with the 1 or 2 refurbished products I ever purchased, I try to avoid them. I purchased a refurbished Phillips 19" flat screen monitor perhaps 20 years ago and today I use it on my security system. If I am going to spend the kind of cash for CPU's or GPU's, I want a new one.
"Refurbished" doesn't necessary mean it has be repaired but returned back to the manufacturer by the Customer for whatever reasons and it was tested and checked good to the manufacturer's standards.
So now the used processor is being sold a "Refurbished" since it isn't brand new anymore. But like I mentioned I never heard of AMD selling "Refurbished" processors before.
Only the Retailers will sell refurbished hardware to get rid of it as a lower price.
If AMD were to replace your AMD Processor with a 3 year Warranty, the Replacement will still have the same 3 Warranty as before minus the amount of time lapsed on the Warranty from the first processor date of purchase.