They offered Poser 11 temporarily, at a reduced price, but no upgrade pricing. You might still be able to buy it here:

https://www.posersoftware.com/store/products/17

There's a 21 day free trial of Poser 12, if you want to try that before you buy. I think buying Poser 11, then upgrading to Poser 12 is slightly cheaper than just buying Poser 12, assuming you can still buy Poser 11.

To try and get your current version of Poser working without Flash, see this thread:

https://www.renderosity.com/rr/mod/forumpro/?thread_id=2956792