when I imported photos they do not show up in the Library view and only show up in the Develop module if I click on a specific photo. All of my existing photos show up correctly, it's only the new imports that do not show up. I looked in finder and the pictures are in the correct folder and the metadata does show correctly in the Library module, but all I see are gray boxes, no photos.
After deleting it, LR will regenerate the previews on demand, which, depending on your photos and the speed of your computer, may cause it to be a little sluggish. You could go to All Photographs, select all photos, and do the menu command Library > Previews > Build Standard-Sized Previews and let it run over night.