UPDATED 9:50PM PDT:
Players who experienced this issue should now have their milestone progress & rewards restored. In addition to this, any earned Champions Arena tickets have been re-distributed. As we realize this was not an ideal experience, we are sending 4 Arena Tickets all players who were impacted by the 21.0.6 arena lockout and the subsequent arena progress reset from updating to 21.0.7. Please expect to receive these tickets via your inbox within the next few hours if you were impacted.
Thank you for your patience and our sincere apologies for the inconvenience.
Team TWD: RTS
We’re currently aware of an issue where some players on Android devices who recently upgraded to the 21.0.7 app version are seeing their progress reset on Arena Milestones and Champions Arena tickets. We apologize for any inconvenience this may have caused and we appreciate your patience as we’re working on resolving the issue. We’ll update this thread with more information as it becomes available.