Every item must have an associated Campaign, so that the proceeds of the sale can be donated to the cause. When you post an item for sale for a Campaign that ends before you can sell it, your item won't be available for sale on Buengo and won't appear on the Items Feed.
To quickly activate your Item for sale again, you just need to select a different Campaign. On your profile, select the Item and tap on "Edit details". Select the "Choose Campaign" field and search for your favourite Campaign from the list.
If you know the name of the Campaign, type it in the search bar. Any campaigns with that name will be shown below.
You can also use the filter tool to look for specific Campaigns. Tap on the filter icon in the top right corner and look for campaigns filtering by category, location or organisation. Tap 'apply filter' to see your results.
Once you have found a Campaign that works for you, tap on "Update Item" to save the changes. Don't forget to share it with your friends so you can quickly find interested buyers.