Cannot work on btop

[coolmian]

Follow the steps in the tutorial to succeed.
But I start another a long running process, btop (it's like the top)
Until the last step, everything was normal.
Finally, I receive these when I run reptyr 133242:

[-] Unable to open the tty in the child.
Unable to attach to pid 133242: No such file or directory

I have tried both tmux and screen.