The same mnemonic used with different paths can generate different addresses. E.g:
Mnemonic A+Path A=Address A
Mnemonic A+Path B=Address B
If you import a mnemonic, you create a new address by changing the TokenPocket's default path (setting a custom path), so be sure to remember this new path. When importing a mnemonic, if the mnemonic does not match the path, the address cannot be found.