can't log in after reboot

I have been having a problem with vitualmin/wwebmin it was working fine but I had to change IP addresses on a virtual server.
After that I could not get webmin to allow login. I have tried restarting webmin but no avail. I had to eventually remove webmin and reinstall this got it working till the next ubuntu update that required a reboot since then the login problem has returned I restarted webmin but no effect. I really would prefer to solve this without reinstalling as it would probably happen again sometime.
I have very limited knowlege but the problem seems to relate to ip address and fully qualified domain name. Any suggestions on how to approach this?

What exactly happens when you try to log in to Webmin?

Uninstalling Webmin is not a good idea when you have Virtualmin installed. It will break a ton of dependencies. Changing the IP address of a virtual server should have no influence on the ability to log in to Webmin, since it uses its own mini webserver.

nothing happens the server simply times out there is no opportunity to log in. At this stage virtualmin is not really being used but I would still like to solve what is the problem.

Okay, this can have a number of reasons. Check if Webmin is running by doing

ps aux|grep miniserv netstat -tpln | grep :10000

Start it with /etc/init.d/webmin start if required.

Make sure you connect the browser to port 10000, and have the right hostname, and that hostname resolves (dig hostname) to the right IP address. Make sure you can ping that IP.

Make sure no firewall is blocking port 10000 (iptables -L -n or ask your hoster if they block ports), or that port 10000 is forwarded properly if you use NAT.

ps aux|grep miniserv

****** 27504 0.0 0.0 9392 940 pts/0 R+ 00:00 0:00 grep --color=auto miniservps

netstat -tpln | grep :10000

tcp 0 0* LISTEN 4277/perl

I can ping the domain or ip

no firewall is blocking 10000

Okay, what’s the actual IP, so I can test it myself? What happens when do telnet IP 10000 from the client where you’re testing it? You could try a different browser / clear the browser cache etc. Did you double-check with iptables -L -n that port 10000 is open?