In digger you have the somewhat misleading option "Additional information visibility". The first option is "Name". You GPX file might contain something like <name>, <cmt>, <desc> and a few more but mostly not relevant. Check the "Name" option behind the GPX values you want to search for.
I am not using a gpx-file for the import, but very simple csv: "longitude dezimal, latitude dezimal,name" ; just coordinates and the identifier of a campsite like
5.233456,40.88888,abc1223 Sunset View
Nothing else. I also tried to use a tomtom-ov2-format as input (which works fine with the tomtom app).
As such that doesn't matter, but did you give the "name" column also the checkmark "Name" in the screen "Additional information visibility" I described?