Maintenance for the week of April 15:
• [COMPLETE] ESO Store and Account System for maintenance – April 16, 8:00AM EDT (12:00 UTC) - 6:00PM EDT (22:00 UTC)
Put them all back into your bank and then back again into your inventory. Should fix it (until the next login).
Not sure if and when the addon author will fix the code.
Also look at the comments on esoui's addon page, someone provided a unofficial fixed version that works.
Edited by anitajoneb17_ESO on August 31, 2019 11:03AM
For me, I had to re-download the add-on. Also, after installing the add-on, open map (M) and go to filters and make sure that
"Lost Treasure Maps" & "Lost Treasure Survey Maps" have "✓" mark & are enabled.