All Box enterprise accounts have the ability to prompt their users to accept the Terms of Service (ToS) before logging in for the very first time.
During a migration, the ToS is problematic because it will block any data upload into a Box user until they have accepted the ToS.
Luckily, a Box administrator can disable the ToS temporarily so that a migration can take place without all users logging in and accepting the ToS.
Click Enterprise Settings via the gear icon on the right-hand side of the menu.
Select Custom Setup
At the bottom of Custom Setup, disable the Terms of Service options.
The Terms of Service may be re-enabled after your migration.
Please note that enabling the ToS will prompt all users, whether they agreed to the ToS already or not, to agree to the new ToS.