The phrase "countless problem" is correct and usable in written English.
This phrase is often used to emphasize the large number or variety of problems someone is dealing with. For example: Jane faced countless problems while organizing the company fundraiser.
Worldwide protest and many authoritative reports highlight countless problems.
Despite countless problems plaguing South America's first Olympics, Rio organisers have been largely successful completing venue construction.
This caused countless problems with friends as I missed weddings, birthdays and big life events because I was too busy.
No one likes to talk about the looming death of a loved one, but asking beforehand avoids countless problems later.
Chile's normally buoyant peso has slid against the dollar too, and the Andean countries have countless problems of their own.
They've seen and learned to deal with countless problems — a torn placenta, an umbilical cord wrapped around a baby's neck, a stuck shoulder.
Six months after President Bush declared that major combat was over, countless problems crowd in on Iraqis, not least unemployment and the absence of security.
Reinjection has caused countless problems in the US and you have to question how far this government will go to make fracking a reality".
Herita Ilunga's foraging runs down the left flank caused Bolton countless problems and both David Di Michele, on 19 minutes, and Valon Behrami, just before the half-hour, sent low shots fizzing narrowly wide from 20 yards out.
One former colleague, Anthony, who spent eight years on the front line of policing, but now works with former gang members trying to get them on the straight and narrow, sent me an 1,800-word 1,800-wordiling countlemailroblems.
