I cam across this on macOS 13.5 (Ventura). Basically Shimo would connect, but then it could not pass any traffic. A reboot fixed it every time, but was painful at times. First thing I did was check the Preferences and enable “Reset Network Configuration when Shimo is terminated” under the Advanced tab. That and pushing the “Reset Network Configuration” didn’t help. This might be the way to stop the issue in the future, but if you are still stuck check out an ifconfig of your interfaces in Terminal. There I found a number of utunX interfaces some that still had IPs even with Shimo quite. I used:
for i in {0..10}; do sudo ifconfig utun$i delete; doneI only had 10 interfaces you may have more, but that got rid of all of the IPs on the utun interfaces without having to reboot.