Hi there,
After updating the T4_bs_blank template I ran in the same problem we already solved quite a while ago:
https://www.joomlart.com/forums/d/43872-how-to-make-the-menu-bar-transparent
After the update again the transparency of the menu bar is gone (the colored header image should shine through the menu bar like this: https://i.imgur.com/7fGHkUi.png ).
Currently it looks like this:
https://stefan-schoch.de
Interestingly the code you suggested and that did the job back then is still present, only the transparency is lost.
What do we have to do this time?