On deployments that include off-site flow sources that use QRadar V6.3.1 or earlier, the upgrade to QRadar 7.1 will fail the pre-test.
QRadar 7.1 does not support pre-7.0 flow sources
Resolving the problem
If your pre-test fails, log in to the QRadar user interface and access Flow Sources window of the QRadar user interface. Remove all pre-7.0 off-site flow sources from the list. These flow sources display Pre-7.0 Offsite Flow Source in the Flow Source Type column. After these flow sources are deleted, your upgrade should complete successfully. If you want to re-add the off-site flow sources after your upgrade is complete, you must install QRadar V7.1 on these hosts.