I answer myself. I put the log and tried to create a user, I realized that I got a permissions error on the folder:
/var/lib/tvheadend/accesscontrol/
I have given permissions with:
chmod -R 777 /var/lib/tvheadend/accesscontrol/
Then I restarted the service:
sudo service tvheadend restart
It seems that everything is solved.
Greetings to all and thank you very much for your help
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