Parts are not automatically being added to assets despite there being a receipt or issue transcation charged to the Asset and 'automatically add parts to this asset' being turned on.
The Parts List on the Asset is not updated until the Resource Transaction (Issue or Receipt) is Posted to Maintenance. This is a long running process that is normally handled by a Scheduled Action.
Since this process is normally run overnight, you will not see the Part on the Asset until the next day.