I have recently changed the nameservers for my domain (from namecheap to yandex) but it's been almost 5 days and the changes haven't been detected over at yandex meaning I can't update the A record. Any ideas why propagation is taking so long? Someone else has access to the domain so I can't be sure whether it has been configured properly. Any help welcome.
It appears that you have not properly delegated authority for the
plantsandbeauty.co.ke domain to yandex.
As with all DNS providers, if you wish yandex to be the "authoritative" nameserver, you need to delegate authority to yandex through the domain registrar in order for the SOA record to be set.
Follow the instructions according to the namecheap KB article, and set
dns2.yandex.net under "Custom DNS." Once you have done that, you can confirm ownership to yandex, following the yandex procedure and selecting the last method, "Delegate a domain to Yandex servers."