The last couple of versions of the FMX UI Pack haven't installed properly. There are no visible errors when running from the TMS Subscription manager but when Delphi 10.2.3 is restarted it can't find the bpl's. Also applies to FNC UI Pack. Manually recompiling the packages works fine.
Please contact us by email and send your installer log files (can be found under \My Documents so we can inspect what happens on your machine.