Hi Aternos team
The Citizens2 plugin can be downloaded for free. There is a link on the Citens2 website (https://www.spigotmc.org/resources/citizens.13811/) were you can download it for free (only the premium version costs money). Can you please install the latest version of Citizens2 from the following link:
https://ci.citizensnpcs.co/job/Citizens2/
Best regards
Lars