There are 2 things you can do :
1. Make sure you choose correct address/import format :
- If your Bitcoin address starts with 1, you should choose P2PKH or legacy
- If your Bitcoin address starts with 3, you should choose P2WPKH-P2SH or P2SH SegWit
- If your Bitcoin address starts with bc1, you should choose P2WPKH or Bech32 or native SegWit
2. Make sure you export you got correct private key from Bitcoin Core, since i'm sure you have more than an address
Also, can you tell us what wallet you used to import your private key from Bitcoin Core?
Tried several methods, Blockchain, Exodus and many more.
My BTC address starts with 3, and when I type dumpprivkey at he console it gives a false key that don't match my address.