Attached is the Northern Ireland nation with the Nicaraguan flag.
Discovered while poking around on the store out of curiosity.

Hello,

I think I know the cause ...
We had to use the ISO code, NI, thinking of Northern Ireland ... but NI is Nicaragua in ISO code.
The Ulster Ban 🏴󠁧󠁢󠁮󠁩󠁲󠁿 , is not recognised internationally, has no ISO code, and therefore no emoji.
The Ulster Ban was used by the government from 1953 to 1973 (before it was dissolved). It is a controversial term, even in Ireland, because it reminds us of a very painful past ... a religious war that led to bloodshed (Sunday, bloody sunday by U2 ... everyone knows, don't they?).

The internationally used and recognised flag is the Union Jack 🇬🇧.
https://en.wikipedia.org/wiki/Flag_of_Northern_Ireland

However, yes, the Ulster Ban is used in certain sporting competitions: Rugby, FIFA, and Commonwealth competitions (until recently).

All that to say, if you want the Ulster Ban, you have to enter it manually.

PS: Tazz26, for the VFIFA list of nations, I've put the Union Jack (because it's more convenient to use emoji, and I'm too lazy to do something manual just for one country ... sorry ...)