I've created a pull request https://github.com/espruino/BangleApps/pull/1167 for the "GPS Info" App that adds the number of satellites in view. On my Bangle 2 I only get a fix with at least 10 satellites in view, which I've never seen indoor (around 5 in view). If a fix "from outside" is available, it continuous working indoor.
Probably the parameters (e.g. the position quality criteria PDOP) for acquiring the first fix are set too high inside the GPS receiver.
Interesting. I have found for Bangle 2 you have to be still in a built up area.
I cant get a fix near my house unless I place the bangle on a dustbin outside or on the window ledge upstairs.
I was out walking the other day and could not get a fix at all when walking. I put the bangle on top of my dashboard when I was changing out my boots and within 1 minute the GPStouch App buzzed to say I had got a fix.