How in the name of all stupid plot devices does each and every space suit, vehicle, structure and other large chunk of habitat equipment not have its own, independent up-link to the multiple Earth-Mars radio relays we already have in orbit around that planet? I squirmed for the first hour because that was too much disbelief to suspend; over the years as habitat equipment appeared on the surface prior to habitation a big collection of radio equipment would unavoidably accrete; they'd be tripping over redundant radio gear.
Yeah, this bugged me, too. AFAICT the overall idea was that they did all these earlier missions to land supplies and stuff, but they didn't have a literal constellation of satellites in orbit to allow reasonable communications? Some of the responses to your post ask things like why we don't have sat phones, etc ... well, there's a difference between a few billion people with communications devices and six of them.
Additionally, mars geosync orbit should be lower, and the atmosphere shouldn't block as much and being 20 years in the future we should have better batteries and antenna and all that. And, even if half of that is wrong, you'd still expect the character in this book/movie to be able to malloc up a sufficient antenna and power to blast a shortwave SOS in the direction of earth.