Many of the Client Response Gallery's headline features hinge upon your images' file names. For this reason, file naming in your Library is of the utmost importance to using the CRG.
Please read our article on file name convention and evaluate the effectiveness of your own convention.
Sadly, Lightroom's handling of file names for virtual copies is very poor. The file names of exported virtual copies differ between the Library Export and the Web Module Export, and neither file name corresponds to image naming in the Library. For this reason, the CRG is unable to work with virtual copies.
If you do need to include virtual copies in your exported galleries, then we advise first that you export virtual copies to standalone files – DNG, TIF or JPG – then re-import those files into your catalog for inclusion in the web gallery. By creating files for your virtual copies, you ensure that Lightroom has an actual file name to work with both in the Library and in any created galleries.