can't reload squid configuration file - lab 12.2

Hi, I got error below when I tried to reload the squid.conf. Is it because that the user account doesn't have rights to the squid process? Please help, thank you!

db@db-Bluebird:~$ systemctl restart squid
db@db-Bluebird:~$ squid -k reconfigure
2022/07/20 10:24:39| FATAL: failed to send signal 1 to Squid instance with PID 39606: (1) Operation not permitted
exception location: main.cc(1748) sendSignal
db@db-Bluebird:~$ sudo systemctl status squid
squid.service - Squid Web Proxy Server
Loaded: loaded (/lib/systemd/system/squid.service; enabled; vendor preset:>
Active: active (running) since Wed 2022-07-20 10:23:38 EDT; 4min 54s ago
Docs: man:squid(8)
Process: 39602 ExecStartPre=/usr/sbin/squid --foreground -z (code=exited, s>
Main PID: 39606 (squid)
Tasks: 4 (limit: 4460)
Memory: 16.0M
CPU: 358ms