GPSMap 66i downloaded geocaching description and hints not available offline

This is not the way to go about getting offline access. Once you have linked the device to your account at geocacing.com, go to Geocaching from the Main Menu (not from setup). 

From the "treasure chest" tab, Menu > GC Live Download. This allows you to then specify a particular GC code OR "download near". Download near allows you to choose a recent find, a waypoint, current location, or a map point. I am not sure how many caches this downloads, but it's more than adequate for day's caching in a high-density area. These are available offline. Not sure about hints (not sure any of the caches I checked had them), but coords, D/T/size and the full description are present. Also not sure about pictures.

From the map tab, Menu > Download Geocaches. I tried this without a fix. Appears to have downloaded near the "current location" on the map. Not clear if panning the map affects the location as you go. These are also available offline once downloaded.

If the device is paired with your phone (Explore app), you can do this in the field (without a WiFi connection, using cellular data and BT). I'm not sure what goes on here. Eventually, I appear to have gotten all of the data downloaded to the device. However, when I looked at the very first cache, there was a pause while details downloaded. I THINK this was just timing - when I later looked at other caches, details were there. But I have no way to tell for sure. When all was said and done, I had all the details on the unit.

You can test all of this by selectively enabling/disabling WiFi and/or BT.

Oh, go ahead. Don't be modest.

https://www.gpsrchive.com/inReach/GPSMAP%2066i/index.htm

Note that some of the detailed information is only available when navigating to a cache.

I did some testing.  Main menu > geocaching > treasure chest tab > menu > GC Live Download > Download Near > my current location (or a map point).  Caches downloaded.  Turn off wifi and return to list of geocaches downloaded.  Select cache (baby maple GC7PQGY) > enter > go > menu > geocache > description = code + owner + lat/long.  Hint = No Hint available.  Compare to geocaching.com in browser and see that further description and hint are available for that cache.  Turn wifi back on, reselect same cache > description….get message that basic members can download details on only 3 caches per day.  This lead me to believe that you don't get descriptions and hints downloaded with a basic membership.  I upgraded my membership to premium and retested.  All the descriptions and hints now seem to be available offline so I'm guessing it was the membership status.

Thank you Twolpert!

Hints and child waypoints are only available when the cache is the destination,  but most other information is available from the map or geocache list. 

I think you have solved that issue. 

Now another website needs to include that information for the next reader!