It sounds like the same issue I was having. After searching through the issues section of the GitHub page I found that the issue has already been reported and the current solution involves compiling it on your computer. The exact steps I followed can be found near the bottom of
this issue.
The issue is that grip is trying to use port 8080 on your network (a port i've found to be rather common among programs I use) and is finding that another program is using it. When this happens, grip crashes and spits out the error that you're getting.