Which version of Electrum are you using?
If it is v3.x you need to use a slightly different menu selection... it is NOT "File -> New\Restore -> standard wallet -> Use Public or private keys". This requires a "Master Private Key" (aka "xprv") to generate an HD wallet.
Instead, you should use "File -> New\Restore -> Import bitcoin addresses or private keys"... this allows you to import private keys in WIF format.
Perfect - Worked fine - Many thanks