Generally certifications are reviewed annually to check that their scope is still relevant. Tasks no longer relevant are removed and new tasks for new features are added.
In your annual renewal, the assessment will typically focus on the new tasks to ensure that your certification is up to date. Typically the annual changes are quote low ~ 5-10% [although I have seen up to 20% change e.g. on AI-900 in the past].
When the scope of an exam changes by more than 33% (it used to be lower), the rule is that Microsoft retires that certification and creates a new certification. Hence simply renewing the old certification would not demonstrate that you have the skills measured, and you will need to take the new exam.
As Gretchen has already replied on
The AI job boom continues: Build the skills that move business forward | Microsoft Community Hub
Microsoft doesn’t offer automatic vouchers or f(r)ee transfers when a certification retires
Microsoft have always retired certifications. I have many more historical certifications than active ones. Five of my certifications are affected by this change and I will be looking to take 3 or maybe 4 of the new certification exams listed.