Just done an install on a brand new Debian11 (Bullseye) and got the same old issue of non starting
Tried all the hints here, not starting
Ran the
chmod +x /usr/lib/influxdb/scripts/influxd-systemd-start.sh
script and got this
/usr/lib/influxdb/scripts/influxd-systemd-start.sh: line 30: curl: command not found
curl is not installed on a base debian.
I am sure someone is going to say RTFM, its on page x, line y 
apt install curl
fixed it.
doing
chmod -x /usr/lib/influxdb/scripts/influxd-systemd-start.sh
chmod o+x /usr/lib/influxdb/scripts/influxd-systemd-start.sh
and it still worked, even over a reboot.
The proper way is to add dependencies to your package and install them prior to your own software.
