Bitcoin Core not showing content of address

Bitcoin core newbie here.
I have an old wallet backed up here, and upon download of the latest blockchain info, importing the wallet, my balance is empty.

Now I do have 3 transactions which I made in 2018, including one on which I transferred all my remaining assets. One of these addresse, upon blockchain explorer verification, indeed contains my asset.

How can I access it via bitcoin core? The wallet was originaly created within Bitcoin Core.
When getting the private key to the address holding my asset, and importing the priv key into an alternative wallet such as electrum, I can’t see the public address holding my assets and not access them either.

Can someone tell me how I can access the content of the public access bound to my private key please?

I spent hours on this already…

cheers