Catalog doesn't link to photos after restore to new PC
New PC, downloaded LR from Adobe, backed up and restored photos. Everything is there just as on old PC but get 'photo missing' message when bringing up catalog. When I go through all the recommended steps in manuals, forums, blogs etc, e.g., locate and find others nearby, LR finds them but they are grayed out as if already imported. Catch 22 -- can't find them but can't re-link them because it thinks they are there.
Food for thought although don't understand why would make a difference:
1) I downloaded new LR software rather than moving copy from old PC (both LR CC)
2) I renamed photos on import (file rename, custom name-sequence) to avoid duplication between memory cards. For example, DSC_0001JPG became KENYA_2016_0001JPG. Again, old PC handles it with no issues.
How can I 're-link' my catalogs to photos master on new PC?
Thanks!