Thank you for your post.
We’ll need a little more information to take action on this report.
What page are you viewing within ARC in offline mode in your screenshot? Did you already attempt to download this particular content before the phone entered Offline Mode?
Do you have this problem with other local library content?
How recently did you sync ARC with your home server? Checking your last report, you mentioned that you often keep the app in Offline Mode for several weeks at a time.
Please verify in ARC Settings that the phone has available storage capacity for additional downloads.