There was a new license format introduced in 4.3: https://www.juniper.net/documentation/us/en/software/paragon-insights/release-notes-4.3.0/release-notes-4.3.0.pdf - Page 3

The old license key format look like this at the beginning:

19 10001 Ni LONG NORMAL STANDALONE AGGR 1_KEYS INFINITE_KEYS 1 DEC 2020 0 0 30 NOV 2025 23 59 NiL SLM_CODE DEMO NiL NiL Ni NiL NiL 15_MINS NiL 0 9qRbo2/0baCWRzToufRU769W4d8OA/E2NtG8MLF8ztofwPEVpnuQw5AstHWwnyWpS0TuPiYiKuRak/Ztw6ZqrvbItbO+iyo1g5kX/h68vJFPBSVXF+SjniDy+/CdB/iNdKKlmj7JpQCN+F9qSMdSi8xTDoMOIABFjkJVzNyq/j+tp

The new license format should look like this at the beginning:

DemolabJUNOS125916403 aaaaaa aaaaaa aaaaaa aaaaaa aaaaaa aaaaaa 
                      aaaaaa aaaaaa aaaaaa aaaaaa aaaaaa aaaaaa
                      aaaaaa aaaaaa aaaaaa aaaaaa aaaaaa aaaaaa
                      aaaaaa aaaaaa aaaaaa aaaaaa aaaaaa aaaaaa
                      aaaaaa aaaaaa aaaaaa

Installation of Paragon 4.3 also requires the user to acknowledge the license change. During installation the below is printed to the cli:

========================== 2 - Checking license state ==========================

Please have a look at below messages and acknowledge them to proceed:

1. Paragon Insights free model/freemium license tier is not available in this version. A valid license (trial or commercial) is needed to use Paragon Insights features.

2. The format of license key has been changed due to business reasons in this version. The system may have contained the older format of license keys, which are not valid now. You can log into the Juniper Agile Licensing Portal and choose to revoke the existing license and then re-activate the license to a new software version (that will provide you with a new format license key). This newly activated license can be added to the system post upgrade.

Paragon Insights License adding failing on format after upgrading to 4.3 with the following message: “License Adding failed: License keys passed as input is invalid”.

In the Juniper Agile Licensing portal, revoke the license and reactivate it. Drop down the version field and choose '23.1 and up'.

If this does not resolve the issue, please open a case with Customer Care.