Electrum supports importing of the BIP39 24 word seed.
I recommend trying this to make sure you have written your seed down correctly.
You just need to start a new wallet, select a standard wallet and state that you already have a seed.
In the seed entry, select options and enable BIP 39.
Enter you 24 words separated by spaces.
Make sure that the status says that the checksum is correct. If it says something else, you haven't entered the seed correctly.
Then Electrum will ask for your derivation.
You need to enter this: m/49'/0'/0'
(instead of the default).
After you have completed, you should see a list of transactions and addresses that you have made with your Ledger Nano S.
Note that the BIP39 seed key can be used to recover all your cryptocurrency, however Electrum only acquires your bitcoin. Not the other coins.