pixel_player40178360
pixel_player68804910
Did you get the ring the LAST time you played this Event & didn't actually clear all the tiles? The game remembers where you left off & it's possible you already collected it. Once the location refreshes, you'll get a ring from it.
https://forum.pixelfederation.com/diggysadventure/d/167896-missing-a-red-ring-in-a-location
If this was not the case, contact SUPPORT regarding not getting the ring.
https://portal.pixelfederation.com/en/diggysadventure/about/
Scroll past the white search 🔍 bar & choose a category to begin the form.
And this Event is ongoing, meaning that only certain mines open depending on your current region. Then the next time Red Rings Event comes aroundaround, you'll more than likely be in another Region & more mines will open for you. (If you complete the Achievement THIS tine, you won't do it again.)
My Egypt Diggy:

My China Diggy:
All the previous mines plus:

Only 2 Reward Mines open.