Other comments indicate that it’s just a free trial that converts to paid at the end. So, don’t worry, you are just excluded from an ad basically.

I wish more ads offered me $1200 of usage followed by the option to either pay to keep using the product or just stop at no cost.

It converts back to paid automatically if you had an existing paid subscription before. No other cases. In any case, this is still a valuable service they are providing for 6mo for free, which many will appreciate even if the goal is to recruit more users.