The most likely issue would be the wrong address type.
Does the address which with the BTC and the addresses in your "new recovered" electrum wallet start with the same character (
1..,
3.. or
bc1..) ?
If not, you need to choose the correct script type when restoring your wallet:
- P2PKH to restore addresses starting with 1..
- P2WPKH-P2SH to restore addresses starting with 3..
- P2WPKH to restore addresses starting with bc1..
I have managed to open the wallet as read-only but it is useless since I cannot operate with the coins we have.
How? By importing the address? If so, this is the wrong approach.
You need to import the correct mnemonic code or private key.