Thanks jwmielsen! And thanks Robert for these great widgets (I'm also using eSearch which is working very well). You were right about Manholes--should have been Manhole, duh. However, now Manhole works but "Sewer Main Line" and "Water Main Lines" (yes, one is plural and the other singular) don't (and "Water Main Lines" was working yesterday when I posted this). I have carefully checked spelling for fields in the .xml to make sure it corresponds with the REST Services pages and cleared the REST cache.
There are actually some other layers that I would like to be able to identify, eg,hydrants and water valves, but when I have "onlythese=false" things like roads, parcels and structures show up but not Water Main Lines, Sewer Main Line, Hydrant or Water Main Valve. All of the problematic layers are operational layers and Manhole is an operational layer that does work. All base layers are identifiable.
Here's the current code and thanks again in advance:
<layers onlythese="true">
<layer>
<name>Water Main Lines</name>
<fields>MATERIAL,LINE SIZE,LENGTH,TYPE,JOINT TYPE,DATE INSTALLED,DEPTH,LOCATEWIRE,GROUND SURFACE,LOCATION DESCRIPTION,COMMENTS</fields>
<linkfield></linkfield>
<linkprefix></linkprefix>
<linksuffix></linksuffix>
<iconfield></iconfield>
<iconprefix></iconprefix>
<iconsuffix></iconsuffix>
<zoomscale>15000</zoomscale>
<forcescale>true</forcescale>
</layer>
<layer>
<name>Manhole</name>
<fields>MANHOLE ID,MATERIAL,DEPTH,RIM ELEVATION,INVERT IN,INVERT OUT</fields>
<linkfield></linkfield>
<linkprefix></linkprefix>
<linksuffix></linksuffix>
<iconfield></iconfield>
<iconprefix></iconprefix>
<iconsuffix></iconsuffix>
<zoomscale>15000</zoomscale>
<forcescale>true</forcescale>
</layer>
<layer>
<name>Sewer Main Line</name>
<fields>LINE SIZE,MATERIAL,LENGTH,SLOPE,GROUND SURFACE,LOCATION DESCRIPTION,TYPE,DATE INSTALLED,COMMENTS</fields>
<linkfield></linkfield>
<linkprefix></linkprefix>
<linksuffix></linksuffix>
<iconfield></iconfield>
<iconprefix></iconprefix>
<iconsuffix></iconsuffix>
<zoomscale>12000</zoomscale>
<forcescale>true</forcescale>
</layer>