This is caused by several different reasons, for example:
* The user is behind a firewall that is blocking ports UDP 4500/500 and/or ESP.
* The VPN client is using connecting on TCP and the default TCP port 10000 for NATT is blocked.
* The internet connection is not stable and some packets are not reaching the VPN concentrator/server or the replies from the server/concentrator arent getting to the client, hence the client thinks the server is no longer available.
* The VPN client is behind a NAT device and the VPN Server doesnt have NAT-T enabled. In this case the user will not be able to send or receive traffic at all. It will be able to connect but thats all. After some time the software client deletes the VPN tunnel.
Suggested solutions:
* If you are using wireless, try to connect with cable
* Turn your firewall off, then test the connection to see whether the problem still occurs. If it doesnt then you can turn your firewall back on, add exception rules for port 500, port 4500 and the ESP protocol in your firewall
* Turn on NAT-T/TCP in your profile ( remember to unblock port 10000 in your firewall)
* Edit your profile with your editor and change ForceKeepAlive=0 to 1
