No tower received

Randomly I don't receive any tower on new rounds. I still have the log message announcing the tower dropped, but nothing in the Inventory

You probably have that tower on auto-transmute. To check you can open the stats screen and long press the tower icon there.

how to turn on and off auto transmute ? i have same problem too

Open the stats screen in the menu bar and long press the tower icon. You can then undo auto transmute for each card.