Hi @nlarenas, and sorry for the slow reply.
You found a real bug, and a slightly embarrassing one: that message was the only error the Order column could show. Several completely different problems all produced the identical “Couldn’t update the order – please try again”, which is why it gives you nothing to go on. I’ve fixed the causes and the message itself in 2.8.6, which is out now.
What was actually going wrong, in most cases:
Your login session token expired. WordPress security tokens expire after 12–24 hours (sooner if you run a security plugin). If you had the posts list open for a while before typing in the Order box, every save would fail until you reloaded the page by hand. Drag-and-drop already refreshed the token automatically – the Order column didn’t. Now it does, invisibly.
Another plugin printing a stray notice. If any other plugin wrote a PHP notice or warning to the page, it corrupted the reply and the save looked like it failed — even though your order had actually been saved. That’s now tolerated.
A brief network hiccup, which now retries once instead of giving up immediately.
Please update to 2.8.6 and try again – for most people this will simply start working.
If it still fails, the error will now tell you what went wrong instead of the generic message. Please paste the exact new wording here and I’ll know immediately where to look.
One other thing to watch for: if the Order column now shows the number as plain text instead of an editable box, that’s deliberate and it’s the fourth cause. It means WordPress reports that you can’t edit that particular item, so the box was previously appearing but every save was being rejected. This usually happens on custom post types registered with their own custom capabilities. If you see that, let me know which post type it is and how it was registered (CPT UI, a theme, custom code?) and I’ll help sort the permissions out.
Thanks for reporting it – this one had been sitting there since the Order column shipped.
