Assuming this is an AMD Ref. design, not one of the partner design models.
If it was purchased through the AMD Store (online), you will have to ship it back to the bro. in law and get him to put in a warranty claim. All details will be under his name/address.
If it was purchased from a retail store (with in law details), then you are considered 2nd owner (no warranty), so posting back to U.S. looks like only option.
My PC- Ryzen 5 5600x, B550 aorus pro ac, Hyper 212 black, 2 x 16gb F4-3600c16dgtzn kit, NM790 2TB, Nitro+RX6900XT, RM850, Win.10 Pro., LC27G55T.