Welcome to what I'm 95% sure is one of the common faults for poorly sealed roof antennas (the fin to the rear on the outside), what most likely happened is water or just the atmosphere over time has broken through the seal between the roof antenna/fin case and poof, no more GPS lock/fix because the electronics are now damaged.
If Presentation Mode is available in your version of software, from the Sat Nav settings menu, we can set our starting position manually and the onboard system will try to track the movements without live GPS as a workaround.
Also, there is one suggested no parts required repair method that I came across in my research of this issue before and that is to try to dry out the fin with a hair drier from just under it or by fully removing it from the roof first.
However, the best permanent fix I've done to date is a replacement roof antenna that was professionally reconditioned and we resprayed the fin it came with to match the car in questions colour code, has been great since.
Pro-tip, even with the new roof antenna it's better to seal the inner edges between the fin case and antenna base, as well as between the base and roof surface with suitable silicone sealer just in case
Then it's just a matter of swapsies with the new for the old damaged fin and an easy DIY on estates/wagons/hatchbacks, not so much on saloons because of the challenging inner access.
That is if this is the cause of the reported issue and hope the above helps