My mother ( does not live close to me) is complaining of a smell in her basement around the area where there is a basement sump pump to pump out water that may seep into the basement.

There was a service person out today and they told her it was most likely because the roof vent was not high enough. They had a new vent put in last year when they had need siding put on the home.

It comes out of the roof but does not go way up. As long as it was up past the roof edge I did not think it could be a issue, is there a required height it has to be above the roof.

The vent should terminate about ten or twelve inches above the roof line.

However, since the smell is in the basement, I'm guessing the ejector basin isn't air tight.

Just a open pit with a sump pump in it, ( been that way for 40 years) and there has not been an odor until just recently.
It pumps the water ( and it only gets water in it about 10 or so times a year, mostly from basement door going out not sealing good.

In years past, there was a sink down there to wash your hands and so, that drained into it, but it had not been used in years.

After the pump sends the water up into the pipe, it has a one way valve that does not allow the water to go back into the sump.

Also the clean out is in the same area about 5 foot above the basement floor but that is normally sealed,

Now I have not been there in several years, but trying to make sure that some repair person does not tell her 1000's of repairs that she does not need.

just a open pit with a sump pump in it, ( been that way for 40 years) and there has not been an odor untill just recently.
It pumps the water ( and it only gets water in it about 10 or so times a year, mostly from basement door going out not sealing good.

In years past, there was a sink down there to wash your hands and so, that drained into it, but it had not been used in years.

After the pump sends the water up into the pipe, it has a one way valve that does not allow the water to go back into the sump.

Also the clean out is in the same area about 5 foot above the basement floor but that is normally sealed,

Now I have not been there in several years, but trying to make sure that some repair person does not tell her 1000's of repairs that she does not need.

I'm not sure where she lives, but if she lives anywhere outside of Georgia, then it's likely been a very wet year for her -- Tell her to unplug the pump, pour in a gallon of bleach and then fill the rest of the basin with water, let it sit overnight and then plug the pump back in in the morning.

Is your mom describing a sewer gas smell or just a very musty odor?

There was a washer/ drayer repair person there today dryer vent issue,
My mom has been complaining for a bit, but then for those who know what I write about her, this is not unusual.

But he said it was for sure a sewer smell and dangerous ( but he also said it was most likely from the vent not being higher above the roof edge.

This is a very high pitch roof ( old style frame house) the top tip of the roof is most likely 8 ft higher to 10 ft higher than the roof edge.
The vent comes out of the basment and though the roof and goes up a foot or so about the roof.

I did not believe it was that but at a loss.

Again I am not there, and trying make sure the height is not the issue before someone charges her $$$ to make it higher and not help

"The vent comes out of the basement and through the roof and goes up a foot or so about the roof" you just described a good vent install. It doesn't need to excede the peak of the roof, just 10-12" above the surface. If mom is up there in years you might want to find a plumber in her area that can check her vent stack. Is there a toilet in this area? Could be a bad wax ring.

Toilet is right above this area ( in the house part) not in the basement, but the toleit is right above this area.