in Bitcoin Core, I don't see the balance.
Blockchain explorers do confirm that address 1PMoUJpj73FUTbjMiKwJfJoo4fJaUE9bTr still holds 8 BTC. So that suggests there has been no hacking or improper removal of money.
first the older key without rescan,
I would re-import the older key with rescan. I would also make sure the wallet has completely synchronised. ...