It seems Emirates is only offering Challenges these days...
Info via Email, 19th of August:
[...] I’m happy to confirm that you are eligible for our Skywards Silver Tier. In order to attain this tier, we will require you to complete one of the two flight options in the coming 12 months:
Option #1: Two roundtrip Emirates flights in Economy class (Flex or Flex Plus fare) OR
Option #2: One roundtrip Emirates flight in Business or First class
Once you have completed one of the two options above, your account will automatically be upgraded to the Skywards tier mentioned.
on August 21, 2019