This happened to me as well. Bought an ocean explorer map and a woodland explorer map from a cartographer. Went to both of those structures holding the respective maps and even held the woodland explorer map as I was exploring inside the Woodland Mansion but achievement would not unlock. I was playing on Windows 10 version 1.16.1 at the time. Have since moved into version 1.16.2 but still no luck.
Happened to me as well on Windows 10 version 1.16.1. Traded with some villagers and now have an XP ball following me that will not absorb.
This happened to me as well. Bought an ocean explorer map and a woodland explorer map from a cartographer. Went to both of those structures holding the respective maps and even held the woodland explorer map as I was exploring inside the Woodland Mansion but achievement would not unlock. I was playing on Windows 10 version 1.16.1 at the time. Have since moved into version 1.16.2 but still no luck.