Not surprising actually, visas are hard, Eritrea is basically African North Korea, and Brexit doesn't help. Hell, Powless missed Worlds last year after his visa came through 20 minutes late, and that was US and Australia
Sudan, DRC, Somalia, lots of countries vying for the title of African north Korea. I imagine travel is easier if you're Eritrean than North Korean (because of differences at country of origin rather than reception at destination).
I any case bini was injured so we aren't missing out as much. Pretty embarrassing for the UK as host not hosting one of the stars of the sport though.