Restoring wallets is a deterministic mathematical process. If you enter a set of inputs, you will always recover the same wallet. If any of those inputs are different from your original wallet, you will instead recover an empty wallet. If you are sure you are using the correct recovery phrase, we identified 3 cases where users can make a mistake.
Case 1 - Most probably it's because you added a BIP39 passphrase when your wallets didn't have it originally. By default Coinomi wallets don't use that option because it's dangerous for new users. Do the restoration process again without enabling the option. Input all 18 words in lowercase characters.
Unless you explicitly added the extra BIP39 passphrase before, the option should be left unchecked. This is not related to the withdraw password you had before (Coinomi will ask you to set that password after pressing "next").
Example: you can test this by recovering a wallet with the Recovery Phrase "area fog genius". When the option isn't checked, you will see the BTC transaction history when adding it. If you enable the option and type anything, you will recover a completely blank wallet.
Case 2 - The opposite is also true. You enabled the extra BIP39 passphrase on your original wallet, but forgot to enable it on the restoration process, or used the wrong passphrase. Do the restoration process again using the correct passphrase. Input all 18 words using lowercase characters.
Having an extra BIP39 passphrase is an advanced option and usually requires extra steps to enable.
Example: you can test this by recovering a wallet with the Recovery Phrase "teach reason poem" and the BIP39 passphrase "t4@P2". If you do it correctly, you will see a BTC transaction history. If you don't enable the option, or use any other passphrase, you will also recover a completely blank wallet.
Case 3 - You added multiple wallets of the same coin originally, and were using a "secondary" wallet (non-default derivation path). Add wallets of the same coin again as many times as you did before.
Coinomi allows you to have more than one wallet for the same coin. Each one is treated as a completely separate, individual wallet. They are always added in an specific order, so if you added 3 at some point, and kept using the third, you will need to add 3 again to reach the wallet you were using.
Note for forked coins (BCH, BTG, BTA): If you added a wallet with the altered derivation path "M/44H/0H/0H" to claim the coins from the fork, you must do so again to see their balance.
Note for NYCoin: If you used NYC with the first 1.8 beta version, add a new wallet setting the derivation path to "M/44H/175H/0H" on advanced settings.
Case 4 - You are recovering from a different, incompatible wallet
Coinomi follows the BIP39 to derive your private keys and addresses. Other wallets, though they might also use some sort of HD derivation method, it could be a different one. Important mentions are the Jaxx wallet when it comes to Ethereum (read more here) and the Electrum wallet (read more here)
Bonus tip 1: If you still have your old phone with your original Coinomi wallet, you can check If you are using the extra BIP39 passphrase by going to "... / Settings / Show recovery phrase". If the option is enabled on your current wallet, you will see a note "This recovery Phrase is protected with a BIP39 passphrase". However the passphrase itself will not be shown.
Bonus tip 2: If you still have your old phone with your original Coinomi wallet, you can check If you are using "secondary" wallets by tap+holding your wallet and choosing "... / Account details". The derivation path of default wallet ends with "0H", following wallets end with "1H", "2H" and so on. When adding a wallet on your new phone, you can specify the derivation path directly, by tapping on "advanced settings"