This issue is resolved.
Some users are reporting problems accessing ICON (https://uiowa.instructure.com) from off-campus internet connections.
ITS is in contact with the vendor about this issue, which may be related to issues with Amazon web hosting.
As a workaround, we recommend using the VPN (https://its.uiowa.edu/vpn) to connect to ICON. Note that you must use Duo two-step authentication to connect to the VPN (https://its.uiowa.edu/support/article/115421).