Solved

building failed to upgrade

What did you try to do?
Upgrade the design building

What happened instead?
Waited 5 days and at the end when I checked it said it was upgrading, then stayed at previous level

Did the bug happen in the app, on PC, or both?
App

What is the model of your device?
Samsung galaxy note 9

What is the operating system?
Android

What is the version number of the operating system?
8.1.0

Can the bug be reproduced?
I've just set it upgrading again but as far as I know it has happened before

Hi Lewis, it sounds like what you saw was the clock showing the amount of time remaining for the upgrade hit zero, or was complete, after which you tapped on the Design building and did not see its level change.

If the Headquarters page were re-visited again, you would see the Design building at its newly upgraded level.

From what I see for your headquarters, there have not been any problems in constructing or upgrading the buildings.