My two border terriers 7 year old dogs have recently taken to not wanting to go for a walk, they simply sit down or just refuse to walk, there have been no scares and no illness, they simply don't want to go for a walk, can anyone help

How cold or hot is it where you live?
My little terrier stopped wanting to go out in the cold as much at around that age.
Dogs spend later years doing a heck of a lot of sleeping. 7 is a little early though.
I assume that they always have water and never are taken on hot concrete or asphalt, or salted sidewalks in winter.

Well I watch a guy for my dog named Cesar Millian and look him up on YouTube like type in Cesar Millian Tips on walking and he will help trust me