prevent device to connect to server

hi
how i can delete device that i authorized to connect to my library ?
i have already delete the device from the list but it still can connect to server
i can not delete the user because i have some device in it
thanks in advance

If you change the password on that account, it should show you a check box “Log out from all connected devices”.

thanks
oki i will test this
it is possible to delete only one not all.

You only delete the device you do not any longer want to have authorized. Due to it having a cache, changing password and forcing a log off will clear the cache. Next time that device tries to start Plex - it will have to reauthorize again.