Custom Post Type ordering no longer working

I’ve been using your plugin for a while now on a clients site of ours, it’s been working great and having made no updates to wordpress or installing any additional plugins etc, it’s suddenly stopped working.

I drag posts up and down to the order I want, then when I come out of the admin screen and go back in they’ve returned to their previous order.
I’ve tried updating to 3.0.2 today thinking this might resolve the issue, but alas it hasn’t.

Is there a reason for this and can it be resolved?

https://www.ads-software.com/plugins/intuitive-custom-post-order/