No trails displayed on the explore app map, help!

Possibly nothing. Depends on where you are located and what maps you have installed in the app. Trail coverage in the legacy Topo North America maps is notoriously spotty. Trails in the national trail system tend to be present. It’s hit and miss for others. 

First thing to try is zooming in and out in an area where you know there are trails. If that doesn’t find anything , I would try downloading the OSM maps for the area. Their trail coverage is pretty good. YMMV of course.

OSM is also available on the Map tab of your account at explore.garmin.com. You can do route planning there, too. However, IMO, the experience is not as good.

You'll need to pay for, and download the good TOPO maps from Garmin in order to get trail data, especially if you want the device to navigate along those trails. There's a reason you get an entire continent of TOPO maps for $50 over the price of the 66s: those maps are missing a lot of useful data.

Garmins 24K topo maps are also missing a lot of information. So much so, I decided to learn how to make my own trail maps as there were none available from any supplier with reasonably current trail data.

I think you are correct. It was a little misleading. How is a buyer, like me, supposed to know there are two grades of TOPO maps from Garmin? It's a litte deceptive. It should have been disclosed. Obviously others are finding the same thing. 

Just purchased a topo 24k for an eTrex touch 35 and cannot be more disappointed to see that everything on the map is way old, including point of interests, trails, roads etc (I mean 6 to 7 years old for some of the point of interests I know well - and no restrooms listed anywhere). I have an etrex 32x and the topoactive (half the price) are actually better and cheaper and up to date (lists restrooms and much more up to date point of interests - but even here some are old, but I can live with it).

If you are interested in trails (as opposed to the location of POIs like restrooms), you may get better results by downloading real boots-on-the-ground tracks from crowd-sourced sites such as AllTrails or GaiaGPS. Some of these are free/freemium and others require a subscription.

Depending on your location, you may also find useful topo maps at gpsfiledepot.com. The maps are crowdsourced and vary considerably by state.

Thank you for your reply, feedback and advise. I greatly appreciated the clarity with which you provided the information which gives me choices. As consumers we should be informed by the seller about what we buy, and in the case of a map what is included and what is not and frankly how old (reliable) the map is and was the last time updated. Again, thank you, Mr. Wolpert, for taking the time to provide useful and clear information to me. On a note, I contacted the customer service at Garmin and they have been extremely kind and helpful as well and they are looking into this matter. I thought it was fair to mention this.