If you see this message, it could mean that there are several problems with your Mnemonic phrase:

1. The backup was incorrect or entered.

2. The format that you entered the Mnemonic phrase is incorrect, there should be a space between each word.

3. Incorrect Mnemonic path.

You can check the problem from the following:

1. You can check the spelling error of the Mnemonic through the open specification, BIP39. https://github.com/bitcoinjs/bip39/blob/master/wordlists/english.json

2. Please make sure the words are separated by space. Do not separate them by a making a new line.

3. Select the default path (the first one)