An advertising interface depends on the settings that the player receives from the advertising network. This also applies to the Skip advertising button – the time of its appearance is indicated by the skipoffset or skipTime parameters in VAST XML.
For VPAID advertising usually all control is transferred to the advertising network module and the player does not control the interface.
If there is no button and the advertising network cannot enable it on its side, add the command [skip:5] to the end of the VAST tag and it will turn on the skip button after 5 seconds. Since version 18.23 this command has full precedence.
You can also use the vast_imaskip:5 parameter in the player code for integration via Google IMA (from v.19.9.22).