Adding Yahoo Sky email to Mailbox List within Yahoo Mail app

[Golo]

I did a quick search and could not see any similar posts.

I am having issues linking my sky.com email (X at sky.com) back to our original main sky.com family mailbox list.

https://overview.mail.yahoo.com/features/multiplemailboxes#1 

There is one sky.com email (lets call it X at sky.com) which I can access separately but is no longer listed since I changed password a couple of days ago and enabled 2FA. I can still access that mailbox separately but it is annoying having to sign out and sign back in to check emails as the yahoo web version does not allow to switch mailboxes like gmail does.  

1. On the yahoo mail app (iphone) when go settings>>manage mailboxes then scroll down to "add a mailbox", then select Yahoo (1st screenshot)
2. It goes through the Yahoo sign in process but then adds the X at sky.com as a completely separate account in the app as opposed to the linked "Mailbox list" (2nd screenshot). 
3. =>This means that both app and webmail version still do not see that X at sky.com mailbox as being added to the group list (3rd screenshot is webmail mailbox list). Therefore for webmail I still have to sign out main account and sign in X at sky.com  to check emails for that mailbox.  

Does anyone know if still possible to add that mailbox like before or somehow Yahoo has removed the ability to connect sky or yahoo mailboxes i.e. only gmail hotmail etc are possible.

thanks!

[Golo]

just realised my screenshot numbering are off but hopefully someone can follow the steps and photos

[Golo]

also as an FYI, i tested using my mom's old gmail account and managed to add her to the mailbox list first time no issues. Just not sure what is going on with the Sky yahoo email.

[Golo]

Me  10:32 PM
Ok quick update - my wife logged into her yahoo.com email account and under "add mailbox" there is Yahoo listed as a mail provider to add yahoo accounts. So I think it is something to do with the "sky.com" powered by yahoo accounts, perhaps a feature which is not enabled for those sky.com accounts to add other yahoo accounts as mailbox.

Yahoo-CustomerCare 10:36 PM
Since this is a Sky account we would be unable to assist with any access issues or errors. Sky uses the Yahoo Mail platform but the back end network is still ran and operated by them. They can be reached directly here: https://help.yahoo.com/kb/SLN25426.html

In short, looks like this feature is no longer available...