Furthermore, when I checked my account, there are only TWELVE (12) phrase words this time instead of my old SEVENTEEN (17) which I actually provided my account password.
-snip-
Is there any other way to retrieve my BTC using my 17 word phrase words?
That 12-word backup phrase is different,
It's your updated wallet's BIP39-compatible seed phrase that is a backup of the new HD keys that your wallet generated as you login to the new version.
Your 17 words backup, on the other hand, is just a backup of your account login credentials. (
Password and WalletID)
If you're expecting any balance from your wallet and if it's not caused by faulty wallet synchronization;
It could be in the non-HD addresses below your "
Wallets and Private Keys" menu in the Settings.
The problem is, if there's no other addresses/keys there; only them
[Blockchain(dot)com] can help you with it since that 'wallet.aes.json' file that's
associateassociated with your login credentials has been sitting in their server and nowhere else.