The beacon installer for 2021 R1.4 (17.4.1) and later requires that .NET 4.7.2 or later be installed on the system. If this version of .NET is not present on the system the launch condition will fail and the install will abort. If the beacon is upgrading, it will continually try to start the upgrade until addressed.
The new version of the beacon requires .NET 4.7.2 or later and if this is not installed the install will abort. When the upgrade aborts, the beacon will constantly try to upgrade and show a message that an upgrade is in progress when you launch the UI.
You can find more details in the FlexNet Beacon.msi.log file found in the Temp folder of the account used to perform the upgrade (which is commonly the account used to run the FlexNet Beacon Engine service). This file will include a message like the following:
Action start 9:26:22: LaunchConditions.
MSI (c) (78:74) [09:26:47:925]: Product: FlexNet Beacon -- Microsoft .NET Framework 4.7.2 Full package or greater needs to be installed for this installation to continue.
Action ended 9:26:47: LaunchConditions. Return value 3.