The bug
If an explorer map leads to a location very near to the map's border, the structure icon won't appear on the map at all.
How to reproduce
Create a world with seed
467491214708786261
Spawn a cartographer:
/summon villager ~ ~ ~ {VillagerData:{profession:cartographer,level:3}}
Purchase a woodland explorer map
→ ❌ The map has no mansion icon
Linked issues
is duplicated by
Attachments
Comments

All right, so the directional thing wasn't a problem. (My seed setup always mixes me up, but that's not a bug--just my human experience with the game. 🙂 ) But, I'm showing some screenshots here that show the map as well as where it's pointing the mansion to, but it's not there. I had a map like this on an earlier version of this world where I was playtesting snapshots and it led me to a similar location where there was no pointer at all, but I did find the mansion on the north side almost off the map. I will go explore there to see if I can find it. If I do, I'll also post a screenshot of that.

Found it! it's up in the corner–same map as on the snapshot phase version. I'm playing on a version of this world that I backed up, in case you're wondering.
Hmm. What's the seed of the world? Where did you get the map?

467491214708786261
Originated in 1.17.1
I got the map from hiring a villager at a village about 3000 blocks south of spawn
If you upgrade the chunks to 1.18, though, it should load in and you can ask or hire any cartographer fairly close to spawn. It's the closest mansion in 1.18, but actually the third one I visited in this world.

Um, in case no one has pieced it together yet, this seems to happen when a structure generates along the edge of an explorer map.
@unknown, please add exact and consistent steps to reproduce this issue, as 'roughly 3000 blocks south of spawn' is a very broad area, and currently it's unclear what is required to do, and what is not based off you describing updating your world.

Happens very often with trial maps in 24w18a

To add to this
I noticed this trend when structure generate (mostly) outside the region of the map so the icon.. Not sure if it was random or not but that's what I gather from personal experience
^^^ As of 24w18a
For a specific repro regarding Trial Chamber explorer maps, see the information provided in MC-271002.

Icon not showing in trial map
Seed: 8
Cartographer in village at: -1091 -256
Map covers: -1600, -576 to -1089, -65
Only trial chamber within range of map is near -1600, -512 (/locate command) or -1591, -521 (chunkbase) - these coordinates cross the map edge, and very little of the large trail chamber actually generates east of -1600 and south of -512.
Edit to add: inspecting the NBT of the explorer map item shows that the location of the icon for the trial chamber is at -1600, -512 ("minecraft:map_decorations" > "+" > ": "rotation":"180", "type":"minecraft.trial_chambers", "x":"-1600", "z":"-512")
Could you please provide a screenshot? Do you use any resource packs?