The NES was really popular, and that means there are lots of consoles out there right now either sitting unused in cupboards or (preferably) still providing entertainment almost three decades after the western release of the system.
However, it's a simple fact that the older a device is, the more chance there is of it developing a fault and not working as it should. In the case of the NES, with it's temperamental spring-loaded cartridge slot, that is likely to happen sooner rather than later. In fact, many NES consoles developed problems with the 72-pin connector back in the '80s — the "toaster" design might have seemed unique when the console was first released, but it's prone to failure.
Thankfully, NES lover and one-time Nintendo Life contributor Joe Walker has the solution: you can boil the 72-pin connector to make it work again.
Needless to say, before attempting this rather unusual fix, you should be aware that you do so at your own risk.