Unfortunately .onion is not a permanent address. All .onion addresses are transient and The Tor Project reserves the right to completely remove support for addr

Unfortunately .onion is not a permanent address. All .onion addresses are transient and The Tor Project reserves the right to completely remove support for addresses whenever they feel it might impact the privacy/security of the tor network. For example, on October 15th of this year all Tor addresses from the last 15 years of Tor v2 will stop being supported and will vanish into thin air.