As all WAVs appear as unassigned, they are not tagged.
You can import them as many times as you want but due to the lag of tags MC is unable to detect Album, Artists, etc simply because there are no tags in the audio file.
The first thing I recommend to do is or enable the tagging of WAV as per
http://wiki.jriver.com/index.php/WAV_%26_AIFF_Taggingor convert the WAVs to a format that does support tagging like FLAC.
As there is no standard for tagging WAV, I do think converting to FLAC and ripping straight to FLAC in the future is your best bet.
If the file structure allows you to select an album you might try
Tools > Library Tools > Lookup track info from online database
My experience with this MC option is that it doesn’t work most of the time.
Maybe you have more luck
If the WAV files have meaningful names you might try
Tools > Library Tools > Fill properties from File name.
If you convert to FLAC you might try MP3Tag.
This requires manually typing the album name for each album.
As MP3Tag uses various internet sources and you are able to tailor your search and get a pick list, this tops the very limited “Lookup track info from online database” option.
If you happen to have the old library you might try rolling back to the old version.
Enable the tagging of WAV and write the tags into the audio.