You can tell if an item is "Active" on eBay if it has an eBayID in the editor, which is displayed at the very top of the eBay section.
You can also use the search filter: "ebayid:>0" to find all items with active eBayIDs.
SureDone syncs these ID's when the item is listed from or imported to SureDone. Once the listing is ended through SureDone, sells out, or expires it will automatically clear out and it can at that point be relisted.
There are two common reasons that the eBayID would still be present in SureDone, but the listing will have ended on eBay.
1) The order has not yet been synced - if your item recently sold it may not be synced yet. It shouldn't take long! SureDone also does a routine check for any missed orders within the past 14 days in case either SureDone or eBay had a temporary glitch.
2) The sync hasn't run yet - for expired listings, SureDone checks every hour to see if a listing expired. It should disappear within 60 minutes
3) The listing was ended outside of SureDone - if you ended the listing directly on eBay or with a different tool - this change will not be reflected in SureDone.
To resolve this problem, you should click "disable" on the item in SureDone and make sure it is ended on eBay as well - from there, if you would like to relist the item, do it from SureDone by clicking "Relist."