Please also see the attached screenshots.

I have just installed Startdrive Advanced V15.1 UPD3 on our PG and (which is not allowed to be connected to the internet).

I also downloaded the Startdrive_V15_1_HSP_FW_V4_7_SP13.zip file so I could update the HW and FW.

The installation of Startdrive went without problems but I cannot install the updates. When I try (from inside the TIA portal it say I have to close the TIA Portal and that the update will start after I close the TIA Portal. But it does not start.

What am I doing wrong and how do I get the updates installed?

Hello xmnj, 

It seems that either you have not close all the tabs of TIA portal and follow following process.

keep support package installation tab as it is and close other remaining tia s/w tabs. then-after (continue) button of package installation will appear . click on it and your package will start to update.