https://www.scodhorpe-united.co.uk/news/2019/october/grimsby-u23s-preview/
This regarding Iron U23s who play midweek
"Clayton Lewis is now back from international duty with New Zealand Under-23s too, so comes into contention."
To me it's looked from the outside like a player keen to return to NZ, and a club prepared to let him go.
He's missed about 8 League Two games whilst away with the NZ U23s in Australia & Fiji. Strange when his club have been struggling at the bottom of the Football Leagues.
They had a look at him in preseason in Oz, but maybe Nix just not interested?