what do you mean by "reindex", and how do I know that it is the correct wallet.dat?
There are two useful options you can add onto the command line as a startup parameter.
-rescan
Cross references all the addresses in your wallet with the block chain and adds missing transactions syncing (balance) with your wallet.dat.
-reindex
Rebuild the chain state and block index, syncing bitcoin core with the network.
If you see your old addresses in the software then you have the correct wallet. Stop and manually start bitcoin core with both options, wait some more, and ideally to return to normal operations.