Hello,
Sorry to hear you are having issues. Here is how you turn and adjust it. Curtains config -> Edit style -> Windows tab-> Advance Property -> scroll down to Explorer background blur mode -> Drop down menu ->Choose blur type and change those within that section colors and transparency level active and inactive mode and also there are different sections between Dark and light mode. Click "apply changes" button to see the changes.
Thank you,
Basj,
Stardock Community Assistant