I can easily restore it, but I can't see the BTC who should be standing there.
So with this you've successfully followed those tutorials.
The problems are the address type and connection/synchronization issues.
For the address type:
If the SEED was created by Electrum, it will immediately recognize its "
type" after you pasted it to the input box.
If it was created by an external BIP39 tool, you need to choose the right address type to match your old address.
- Select "legacy (p2pkh)" if your previous addresses starts with "1".
- Select "p2sh-segwit (p2wpkh-p2sh)" if it starts with "3".
- Or select "native segwit (p2wpkh)" if it starts with "bc1".
For Connection issues:
- At first run, Electrum requires to download the "block_headers" file to display the correct balance and transaction history.
Even synchronized the balance will not show up if it wasn't downloaded yet (about 44mb+). - Read the other replies above for more possible causes of connection issues.