As I've said in the shoutbox, if it's a visa, then it's likely down to the general delays at UKVI (lots of staff moved to teams processing Ukrainian visas).
We've had students delay arrival because they didn't get their paperwork back in time because turnaround was longer than normal. Absolutely nothing you can do to hurry the process along.
There are also conditions to be met to qualify for the visa, one of which is an internationally recognised certificate of English language attainment. As these have to be carried out in certified test centres, there can be a delay here too especially when a shit ton of students are also getting tested/re-tested in order to get across to the UK for term starting in September.
Also not sure how they define living in a country for the mandatory TB test for certain nations. If he still has a home in the Ivory Coast, it might be that this has to be arranged.
Apply for an International Sportsperson visa if you're an elite sportsperson or coach with sponsorship - getting sponsored, eligibility, documents, extend your visa, family members
www.gov.uk