Why can't I use the gold snake treasure map bought by the old beggar who ran out of the hero's altar?

The treasure map of the golden snake bought by the old beggar who ran out of the hero's altar cannot be used because the hidden plot has not been completed. I don't want to talk to anyone after I bought the golden snake treasure map from the old beggar who ran out of the hero's altar. Go to the right corner of Tongnan Inn and walk against the wall. Use the vase in the lower right corner of Tongnan Inn to complete several hidden plots, and then you can use the Golden Snake Treasure Map.