WPML support?

it reverts back to the default order-

not sure what you mean here. The order is stored in a unique meta-field, the only way for it to be reset it is the database table itself is wiped or the WPML plugin is interferring with the DB query, in either cases that would be a bug with the WPML plugin.

I use Polylang plugin for multi-lingual websites and it works just fine.

WPML works in a similar way to Polylang, saving translations as separate posts and tagging them as such.

When you create a taxonomy for your posts, you need to make sure you tanslate the taxonomy terms as well. I reckon this is where you have gone wrong.

Can you confirm if you have translated the terms of your posts?

I was just hoping that if I ordered the English posts that it would automatically order all the other languages, but I guess that is not possible?

no currently it is not possible, it requires quite a lot of additional coding to achieve this.

Will you be adding WPML support?

unlikely, unless someone wants to sponsor it.

I develop general plugins (such as this one) for my projects, the effort that goes into design/implementation is paid for by my clients. I fix bugs for free.

In the future it is possible such a functionality is required on one of my projects, but it will be most likely be with the Polylang plugin and not the WPML as I don’t use it and likely never will.

So if you really need this fuctionality, I could develop it if you want to sponsor it 🙂