So, I've done everything as you wrote, step by step...installed using online installer, but the file system shield still appears not to be working again. Anyway, I noticed that when installing older avast versions, exclamation mark does not appear, even though the file system shield is not active nor can be turned on. It all looks like avast file system shield *.dll file is missing or something...do you maybe know if there is such file in avast folder ? I've checked every single .dll file's description in the folder and none of them says File System Shield, while there are *.dll's for both web and mail shields...I will put the pictures of what avast folder contains below, in case you know what could be missing...
Thank you very much for your time and help...I appreciate it a lot.