The page /web-admin/ should be managed by nginx (base server for Headwind Remote), not by Tomcat.
When Headwind Remote is installed on the same server with Headwind MDM, nginx works as a proxy for Tomcat, see this diagram:
If you see Tomcat's response 404, it means that nginx is not accessible on port 443.
The most probable reason for that is the port redirection (443 -> 8443) by iptables, which is the default option of Headwind MDM installer.
To check whether iptables redirect the traffic, run the command:
iptables-save
There is an active port redirection, if you see the output like this:
-A PREROUTING -p tcp -m tcp --dport 443 -j REDIRECT --to-ports 8443
-A OUTPUT -o lo -p tcp -m tcp --dport 443 -j REDIRECT --to-ports 8443
Remove the redirection by running the commands:
iptables -t nat -D PREROUTING -p tcp -m tcp --dport 443 -j REDIRECT --to-ports 8443
iptables -t nat -D OUTPUT -o lo -p tcp -m tcp --dport 443 -j REDIRECT --to-ports 8443
This should resolve the issue. If it doesn't, try restartng Headwind Remote by running commands:
cd /opt/remote-control
bash ./install.sh
Make sure iptables are not started at boot (another default option of Headwind MDM installer).
Run the command
crontab -l
If you see the line
@reboot /opt/hmdm/iptables-tomcat.sh
Remove it from crontab (or comment it out by # character) by using the command
crontab -e