Yes, you can re-open your Help to Buy ISA if your home purchase fails. To do this, you'll need a Purchase Failure Notice (PFN) which you can get from your solicitor. You'll also need to ask us to re-open the account within 12 months.
You'll be able to save into your Help to Buy ISA until 30 November 2029. After that, you'll have until 30 November 2030 to claim your bonus.