GPS "ring" on watch never turned green (it turned orange instead) but it worked ...

No, orange is not the new green. Orange is indicates that the GPS is not fully connected. If you had waited a little longer it probably would have changed to green. It is possible that you need to ensure you have an up-to-date .epo file if it's taking a little longer than normal to synchronize.

When these colour rings first came to the Fenix 3, the software notes mentioned something about the Amber ring being the minimum for horizontal position by GPS and the Green ring being a good enough lock for vertical position too, so that the watch can auto calibrate altitude at the start of an activity. The general rule of thumb is wait for a Geeen lock as a minimum before moving off if you can.

Thanks, folks.

That was the first time ever it didn't turn to green in just a few seconds. I waited probably 60-90 seconds and it never turned green, even trying some of the other Go so cookout usually use. Maybe it was the solar flare that hit the earth yesterday that messed up GPS (though perhaps unlikely if I'm in only one with problems).

Very interesting that when Orange/Amber the altitude lock isn't as good, thanks for that info, Crispen_Ellisdon. The altitude map looked good, so maybe it kicked in after a bit of running.

Philipshambrook, I'm not quite sure what a .epo file is: "It is possible that you need to ensure you have an up-to-date .epo file if it's taking a little longer than normal to synchronize."

But I will Google that if the problem recurs, thanks!

Epo file contains satellite position data to improve locking time. Usually updated when you connect to your mobile phone or Garmin Express.

In many cases waiting another 30 seconds or so past green seems to help tracking during the start of a run. It particularly seems to help altitude calibration.

Before the coloured rings, the best method to ensure a good lock before moving off, was to have the Pace data field somewhere on the first data screen and wait for pace to drop to zero (so eliminating the ‘jumping around’ whilst position is zeroed).

For the EPO data, if you go to "About" and scroll down toward the end, you'll see the state of the EPO data - you want it to be current.
EPO data is only valid for a matter of days:

https://support.garmin.com/en-AU/?faq=6IbaJEHc1i9gydzQomXzyA

Extended Prediction Orbit (EPO) files allow GPS devices to predict where satellites will be in the sky, which reduces GPS acquisition time. With updated EPO files on a device, instead taking 2-3 minutes to find GPS signals, it will usually take 5-10 seconds.

EPO files expire, and are usually only good for a range of 3-14 days. In order to keep the EPO files updated, sync the device regularly.

Well that is very interesting indeed, thank you jim_m_58!

As it turns out, without any intervention on my part it locked into GPS and I got a "Green" within moments of going outside today. I sync daily, so who knows what caused yesterday's problems. Unless proven otherwise, I'm going to have fun saying it must have been that big solar flare activity I read about!

Thanks again, j im_m_58!