Mac install on sequoia 15.4.1

I installed syncthing on my MAC. It worked once. It will not start anymore. The application is running. When I attempt to start it, it opens Safari and inserts the 127.0.0.1 without the port information (:8384). I have tried turning off my security suite.This does not work.

Safari reports 127.0.0.1 as a dangerous site and will not connect.

I have tried deleting the app and reinstalling it. Same result.

I would appreciate any advice you can offer me..

What exactly did you install? Bare Syncthing, or the Syncthing-MacOS wrapper which provides a notification icon for interaction? Screenshots of the actual error message / browser window would help.

Maybe Safari is just hiding the port information as too technical for the average user? Have you tried manually entering the URL including the port?

A security warning for the page is usually no concern. It uses a self-signed certificate, which is okay if you’re accessing it locally on your own computer. You could even try http instead of https, which uses no certificate at all and doesn’t give that warning. But please do that only in a trusted environment, i.e. on the same host (or a trusted network if you have enabled external GUI access).