Hello,
It seems that you are using legacy firmware version. There should be an option in IPSec settings to allow WebUI access:
If this does not help, you can try resetting the device to default settings via reset button or from the WebUI. Since the issue appeared after firmware upgrade, it is possible that there were some migration issues.
Also, the firmware is quite old. Is there a reason why you are using this version? If feasible, I suggest you consider updating the firmware to the latest version. Firmware for RUT950 can be downloaded from here.
Kind Regards,