Some Thunderbolt- or USB-C docks might not support the function, to power on the connected PC via the dock's power button. For example, dock's like the Thunderbolt 3 dock (PA5281E) or dynabook USB-C dock (PA5356E) do not support this function (or only on particular PC series - please see related document Supported features by platform).
Infographic show dock's power delivery PC connection
Mostly this is caused due to the fact, that the dock's power button is only a on-/off power switch of the dock itself.
As alternative method, enabling the BIOS setting "Power on by AC" can bypass this technical limitation.
For details of the "Power on by AC" BIOS setting, please refer to the picture shown in the "Resolution | Detailed" setting below.
Please refer to the below picture, which is showing the PC's BIOS setup utility "Power on by AC" setting:
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