Private key not corresponding to address? Need Help!

[Sogeking]

When importing my private key in www.omniwallet.org or when I enter it in www.bitaddress.org it shows a different address than my electrum.
It is about the following address (in electrum) : 3Jnz4bDfgmB9DYiZkxZX53rnYyWb3XG2pQ.
I read somewhere that an address starting with a 3 (is p2sh? and) can have multiple private keys and that it is possible that I have the wrong one. How do I retrieve the right private key corresponding to this address? Thanks in advance.

[Swagtoshi]

Some addresses that have multiple private keys.

It does not matter which private key you use. All the private keys will work.

[Sogeking]

I accidently put MAID into my Electrum, so I think that is the reason why my private key does not correspond to the right address. When I check my address on www.omniwallet.org it shows the right amount of MAID, but when I import my private key it shows a balance of $0.00 and gives a whole new address.

[HCP]

It is about the following address (in electrum) : 3Jnz4bDfgmB9DYiZkxZX53rnYyWb3XG2pQ.

Is your Electrum wallet a Two Factor Authentication (aka "2FA") wallet? "3" addresses in Electrum are usually from a 2FA wallet... but can also be from a "MultiSig" wallet. These addresses actually require multiple private keys to be able to send coins. They cannot easily be "imported" into another wallet.

A "3" address from an Electrum 2FA wallet is a "2of3" MultiSig and actually has 3 private keys. 1 key is controlled by TrustedCoin (you need a Google Authenticator code to get them to sign a transaction), the other 2 keys are controlled by your "seed words". By default, 1 of these seed words keys is stored in the wallet file. This is the private key you get when you "export" the private key from Electrum.

The 2nd private key is only stored in your wallet if you restore it using your 2FA seed words and choose "DISABLE" when prompted to keep or disable 2FA functionality.

Any combination of 2 of these 3 private keys will be able to sign a transaction that is able to spend coins from the address. However, you will struggle to be able to recreate your "3" address in another wallet unless it allows creation of MultiSig Addresses and even then it won't be easy.

Some addresses that have multiple private keys.
It does not matter which private key you use. All the private keys will work.

That is incorrect.