Not A Bug Problem New Earth 31 century

Why after the new flashpoint update i can't enter the 31st century metropolis anymore?

Yes

But there isn’t anymore New earth 31 century

tells me I have to purchase the episode

Why?

Is your character below cr 310 and have been playing the event version of instances?
Since the event version of the Legion episode is over, characters who don't meet the minimum requirement to complete the normal version of such content will be locked out of open world as well.

My character cr 321

now in the warp menu instead of New Earth 31 Century there is Flashpoint Gotham

The warp menu only includes episode warp to the latest episode's open world that is the norm for sometime now, so yes they intentionally hid the warp for 31st century. If you want to go there just use the teleporter in HQ or base teleporter with Urgent Warfronst mod on.

No i can’t because it tells me that i have to purchase the episode now....but why if my character cr is 321?

Normally episodes are locked after the event ends and only accessible if you either:
1. Own the episode and are the appropriate CR to enter.
or
2. Have an active subscription and are the appropriate CR to enter.

If you don't own the episode or have an active subscription you are going to have to wait for the devs to add Long Live the Legion to the current open episode event: https://www.dcuniverseonline.com/news/dcuo-open-episodes-bonus-weeks-march-2020

Ok thanks, i didn’t know that, so i must wait

Thanks a lot!