Hello,
the problem that I have is that the program itself works, but can not by open from the Application folder with all installed programs. Also the avast logo in MenuBar is not visible. I can not open the program itself in any way! It is not a problem related with dark/light mode. Before it did not have this problem. I have Higt Sierra 10.13 installed and Avast 14.3, maybe it's the last version you have right now.
I do not understand what the problem is and how to fix it. And I repeat again that the program in itself works.
best regards