Cannot see my map in configure maps on my Montana 750i.

Conventional wisdom is to remove the card, boot the unit with the card out, power down, reinsert the card, boot again. This should force the unit to reindex the maps.

Same problem here on my 700i. I tried using Garmin Express to transfer Topo Southwest 24K, newly purchased, to the 700i. It took 20 minutes or so, showed up on the Micro SD in the Garmin folder (3.07G) but won't show up under Configure Maps. Saw there was a firmware update for the 700i, as well as Garmin Express. I updated both and tried once again to move the purchased file to the 700i. No change. I ended up contacting Garmin Support, who called right back. There is a ticket open on this issue already from other owners. Apparently, there is a problem with Garmin Express, not the GPS. It would be a week or so before the problem gets worked on by the appropriate personnel. Hopefully, the next Garmin Express update will cure the issue. I was relieved to learn it wasn't the 700i or my ineptness!

Though if your map was on a pre-loaded MicroSD, would it even need Garmin Express? I've never used a pre-loaded map

Tried your suggestion twolpert but it didn't resolve my missing Topo issue

It would appear that it’s a map compatibility issue in that the 1:25k isn’t on the map list but the 1:50k is ??

Strange....

You don’t need or want Express if the you purchased the map ON the card. Such maps are locked to the card, not the device on which first installed. The card cannot be successfully copied.

OTOH, if you purchase a map via download delivery, you can certainly install it to an SD card rather than internal memory. In this case, the map is locked to the device in which the SD card was inserted during the first install.

Hmmm....perhaps the map not appearing on the Configure Maps list IS a GPS bug, not Express. I found it strange that Express told me the Topo download MAY end up on the SD card. There was enough space in internal memory for the file(s). I was expecting it to ask me where I wanted it copied to.

 I’m assuming the downloaded Topo is locked to my 700i. I can select it on Basecamp but when I do I just see the map without waypoints & tracks overlayed. I’ve only ever used free maps on my past Garmin handhelds so I’m thinking Basecamp is behaving as expected with my purchase.

I had the same problem. I have OS Pro 1:25k1:50k micro SD card when I installed it the OS map would not show up so I turned all maps off in map configuration except OS maps and it still didn't work. I turned all the maps off turned the unit off and on then OS map back on and it started working hope this helps.

You got my hopes up and I tried all manner of disabling maps, resetting the 700i, cycling power, card in card out. No joy, however, as my purchased/downloaded Southwest Topo 24k still won’t show in Configure Maps. It’s there on the upper left, in Basecamp. I can select it and Scroll around on the map

Hopefully, you’ve solved the OP’s issue and perhaps Garmin Support’s suggestion that my problem is an issue with Garmin Express is accurate.

As long as you're torturing yourself with BaseCamp, have you tried installing the map through the map manager that's part of the BaseCamp package? Be sure you have the most recent version. There was a long-standing bug which delivered only thumbnails, not the full map. It has been fixed in the most recent release.