Hi, @hc02ca!
Sorry, your message took me just while I was getting on bed.
The hosts file is OK.
I'm as lost as @yanokwa.
- The most interesting hint you've given us is that Briefcase thinks that the URL https://sandbox.aggregate.opendatakit.org/Aggregate.html somehow is equal to http://127.0.0.1:8081 (or it's being redirected to that address).
- The sandbox appears to be OK (I believe @yanokwa rebooted it some hours ago) . I've been able to pull all forms right now.
This scenario leads me to believe that something in yout computer's networking configuration or on the network you're on is wrong.
- Are you running any networking app like or using a VPN?
- Could you try a wired connection or change to another WiFi network?
- Could you open a browser and try opening http://127.0.0.1:8081 and https://127.0.0.1:8081 and see what's there?