I created a legend, then changed the symbology of one of my layers. I used the Expression Builder in the Symbology pane to create custom symbology and the layer disappeared from my legend. It is listed in the legend tree in the Contents pane, but isn't showing up in the legend. I deleted the legend and recreated it, and the layer still isn't showing in the legend. Any thoughts?
I had a layer disappear from the legend. I copied and pasted it (then had to adjust the formatting of the patch to match other layers), but at least I was able to fix the legend issue. (2.2.1). I don't have time to try to reproduce the bug; hopefully someone at ESRI can track it down. (I had restricted the legend to showing only symbols for features w/in the map extent, and added the layer after that, so perhaps that was the problem?)
The only scenarios where layers should disappear from the legend are:
I'm not aware of any outstanding issue where legend items unexpectedly disappear from the legend. Unfortunately, if you are experiencing a bug we would need more information to investigate further.
You mentioned that you are doing some copying and pasting. If you are copying and pasting layer elements (such as map frames and legends) make sure that the pasted element is referring to the correct map ( in the case of a pasted map frame) or map frame (in the case of a pasted legend). You can find this info in the Options tab of the properties pane (Format Map Frame & Format Legend).
Hope this helps.
The issue is that if syncing w/ new layers is OFF for the legend, and a layer is added, I have not found a way to add that layer into the legend (without removing it and adding it back in while "Synchronize with map --> New layer" is on). Below, I created the legend when only Cities was in the map. I then set the US Cities layer to only show features visible in the map extent, then turned off the layer sync in the legend properties. I added the Counties layer. When I re-check the New layer option for syncing, the legend remains limited to US Cities. If I spent a lot of time formatting the legend while "New layer" was unchecked in the Sync options, and added a few new layers, the workaround of deleting/re-adding the layers would make more sense than creating a new legend.
If the "New layer" option is checked off you can add new layers to the legend by either dragging and dropping the new layer from the map portion of the Contents Pane into the legend portion of the Contents Pane or onto the legend element on the layout view itself.