If the wallet address generated by importing the mnemonic phrases is a new wallet address that does not match your expected one, there are 3 possible reasons. We recommend that you check them out one by one.
Reason 1: You are using mnemonics of a different account or some words are incorrect or in a wrong order.
Reason 2: Select the wrong address type at the recovery step(Segwit or non-Segwit)
Reason 3: If you added a passphrase when you created the account, please add it when you recover the account. If you don't add or write the wrong passphrase, the address will be different.
You may simply check by XRP address, If the XRP address is the same but other coin addresses different, The reason is number 3.