Email campaign trial period ended? A new subscription?

Hello, thank you for the great support always.

Recently I noticed that I can no longer send a newsletter from squarespace.

I have been paying for a business plan (24 euros+tax) for the last some years and never realized that sending a newsletter 4 times a year isn't included in the plan.

Now I am asked to upgrade to either Starter, Core, Pro, Max account. Is this something additional I must pay to the current Business plan? Or am I starting all over to change the plan from scratch?

Since I already have the domain, I'm wondering why I can no longer send email to subscribers and what change I must make.

Looking forward to advice.