Lack of reviewers in Nigeria
Nigeria has the largest population in Africa and is as well becoming the tech capital of Africa. Nigeria's median age is also just around 18 years which in my opinion is a prime, untapped market for Pokemon Go and other Niantic games. Sadly, Nigeria is still under-represented in Pokemon Go. The biggest issue is the lack of reviewers due to the lack of Wayspots in the country. As a result, not enough people can reach a high enough level to review, and even if you could, you would still not find enough reviewers in your country.
So, it'll be super helpful if Niantic can devote more resources to Nigeria and maybe suggest a Nigerian/African Wayfarer Challenge.