I can reproduce your problem on my windows 10 system. And I think I might have a solution for you.
I am assuming you have Start10, Windowblind 10 all applies and all good except the "no blur problem".
1. Try disable windowblind by applying Windows default theme. (do not uninstall windowblinds)
2. Open Start10 configuration windows, goto "Desktop" setting and make sure "Blur the wallpaper under the taskbar" selected select your transparency as you like. (note: this whole section will be grayed out if you have windowblinds active.)
3. Apply Windowblinds theme again. And see if that solve your problem. It did on mine.
Let me know the outcome.
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