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When did he last work on your home?
He cannot register a lien. The lien had to be registered within 45 days of October 4 and it was not.
He can sue you and you will defend of course but the lien is a non-issue.
You can tell him or the collection agency that is he sues you not only will you vigorously defend but you will also counter-claim as he has cost you more than you paid him and will also be seeking damages for the poor work, inconvenience, interest and your legal costs.
And if it gets that far you can always post on this site and I can assist you further as this will be in Small Claims Court and you can self-represent.