We'll be upgrading our North-American server next Sunday (the 17th of March).
This means a downtime for about 10 hours, starting at 1AM EST (6AM UTC, 2AM EDT).
During this period, the following functions will not be available:
2. Coupons will not be obtainable
3. Tile updates will be suspended for 1-2 days in the NA server
There is also an announcement on the Status page
*update* - the upgrade was completed successfully.