You say you imported your catalogue. Normally LR6 will offer to upgrade, not import. So exactly what menu commands did you follow? Did you "import" anything?
It might be worth opening Lr5 and checking your catalogue had the metadata. Then take a note of exactly where this catalogue is located (in Catalog Settings) and make sure it is this catalogue that you are opening in LR6. It will then offer to upgrade it. At no time should you be "importing" anything.