You need the password to decrypt it. If you don't know the exact password but have some idea of what it might be you can attempt to bruteforce it. That means to try various combinations of passwords until you hit the right one. You can bruteforce it using btchris' script given below or hire someone to do it for you:
https://github.com/gurnec/btcrecoverHowever you must have at least some idea of what the password might be for bruteforcing to be feasible.
I also attempted to use the decrypt_electrum_seed code from GitHub but kept getting the messages unexpected seed_version: 13 and KeyError : 'seed'. The same error is produced by wallets that have a password and wallets that don't have a password so do you have any idea what else might be causing these errors?
I think the file mnemonic.py on the decrypt_electrum_seed page possibly contains the words the code uses to try and decrypt the wallet but I could be wrong. If this is the case then the problem may be in the fact that some of the seed words Electrum generates when new wallets are created are not contained within the mnemonic.py list of words?
But the code might be using a more up to date list than the one shown in mnemonic.py and the problem might be being caused by something else.