Hello schade,
Please read the following the following information:
License Key Exchange — To use the licenses for vMX and vBNG features in Junos OS Release 19.2R1 and above, you need new license keys. Previous license keys are supported for previous Junos OS releases, but for Junos OS Release 19.2 and above releases, you need to migrate existing licenses (one-time activity). Contact Customer Care to exchange previous licenses. Note that you can choose either to use individual license keys for each device or to deploy Juniper Agile License Manager for more efficient management of licenses.
It is not mandatory to install the Agile License Manager to use vMX or vBNG licenses on Junos OS Release 19.2R1 and later releases. The Agile License Manager is a new option that provides more efficient management of licenses. You can continue to use individual license keys for each device if required.
Existing license keys are not supported on Junos OS Release 19.2R1 and later releases. Contact Customer Care for exchanging previous license keys.
https://www.juniper.net/documentation/en_US/release-independent/licensing/information-products/topic-collections/release-note/jd0e30.html#jd0e30
Such behavior is expected since license is not provided, you may reach Customer Care for more assistance on the license.
Also, I see that BNG for 10 subscribers is under the vMX Premium licenses: https://www.juniper.net/documentation/en_US/release-independent/licensing/topics/topic-map/vmx-licensing.html
If this resolve your question/issue please mark this response as "Accepted Solution"
Kudos is always appreciated!