"Representation: Unknown" appears in place of the list of representations in the TOC. In the process of setting up or editing my maps, my various feature classes will 'lose' the representations and show the quoted text above. The representation still exists in Properties>Symbology but will not appear in the TOC. I can get the representations to reappear in the TOC by opening properties and adding an additional generic rule (or loading an existing rule), but when I apply the change and close the properties, the TOC reverts to "Representation: Unknown". Likewise, when the TOC reads "Representation: Unknown", the symbols do not show at all in the data frame or layout. In some sense it is 'musical chairs' in that I can get one feature class representation to function properly, then another one will revert to "Representation: Unknown". I have found no instances of this in the forum and hope that means that I am overlooking an obvious fix. I have spent considerable time implementing representations and want to make full use of them.
Please speak up if you have encountered this behavior, thanks.
This is a description of what I have been doing to "fix" the issue. Late last week I did as you described and got the "musical chairs" behavior such that when I fixed one, another layer 'broke'....fixed that one and the first 'broke'...and on.... Today, I reset the representations and, for the moment, all layers are working. I don't expect this to last but I need to get work done.
Anyone else with a 'ritual' to fix this issue, please post. Thanks