There are changes that have not been assigned to a transport request

What causes this issue?

You have changed one or more start conditions. These changes are
already active, but it has not yet been possible to assign them to a
transport request.

How to fix this error?

If you want to transport the changes, select <PF>Transport</> and
specify the transport request required.
If you do not want to transport the changes, you can exit the start
condition transaction with <PF>Cancel</>. The changes are then not
transported on to other systems and/or clients.

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.