Conditional formatting for cell based on self matches one from another column/tab/sheet using Apps Script
Solution 1:
Should be pretty straightforward. New tab on your shared sheet called MK.Idea with this cond. formatting rule:
=ISNUMBER(MATCH(D1,INDIRECT("Blocked!A:A"),0))
Note: Could you mention where you got/how you constructed your other attempt? Appscript is definitely not necessary, And it would be good to correct the record at the source.