VLOOKUP function #REF error

I have a spreadsheet with multiple pages that all reference the first page.
1st page) mast list of all real estate properties with categories of data
2nd page) everything is categorized from the building class (a, b, or c)
3rd page is where i want the VLOOKUP function to occur.

on all the pages following the first page i have it automatically pull the name so it doesn't have to be typed out everytime.

what i want to have happen on the third page is have it look at the name of the property in the B column, compare it to the name on either the first or second page and find the match, then go over x columns to find the building class so i can use it within a formula to find the average percentage of each building class.

my formula i'm trying to use it:

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B4=the name of the property on the third page. it's what i want the vlookup function to find on either the first or second page
'Units by Class'!B3:30 = the page and column of where the names are located on the second page i want it to search through
7 = the column of building class letters that i want it to identify and spit out

what am i doing wrong?