UPDATE: I posted the message below yesterday, having tried unsuccessfully several times to get the one item I mention in the message to sync. However, today I synced again, and this time everything synced, including the one that wouldn't do so yesterday. So I think the problem was short-lived.
I've been using WhenLast and loving it. Today, however, I noticed a small glitch. Most of my categories have several items, but one category has only one. The category is called Tablet and the item's label is "Unchecked permit sideloading." I sometimes install apps from outside the app store, and to do that I have to check a security setting that permits sideloading. After I've installed the app, I need to be sure I've unchecked that setting. Today, I did a manual sync between my tablet and my smartphone. The tablet a few changes. All apparently were uploaded to dropbox, but when I did the manual sync with the smartphone, all were synced except the "Unchecked permit sideloading" item. I looked at the history of syncs involving this item, and it's the same on both devices until today. I tried again to sync, first between the tablet and dropbox and then between the phone and dropbox. But that item remains unchanged. The WL date on the tablet is 03/21/2015, while that on the phone is still 02/09/2015. I can't think of anything else that might be relevant, except that the Tablet category is the fourth of four categories on the phone, but the third of four categories on the tablet. I wouldn't think that would matter, but I thought I'd mention it anyway. I should add that I'm using v. 1.84 of WhenLast on my tablet running KitKat 4.4.4 and my phone running KitKat 4.4.2. If there's any other information you need, please let me know.
Thanks in advance for your help.