How to retrieve names from the table? 2 criteria given

Hi all! I'm working on KPI for my company. Unfortunately I struggle on one formula. I want to retrieve names of staff who are on holidays or sick. I made a formula and am sure enough it should work, but it doesn't. All I get is #REF, #NUM, and #NA errors. See attached workbook. Maybe someone will find a solution... More info inside the workbook. Thanks in advance!

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try thid out in Main Sheet
=LOOKUP(REPT("Z",255),CHOOSE({1,2},"",INDEX(Staff!$A$31:$A$51,SMALL(IF(OFFSET(Staff!$A$30,,MATCH(MAIN!$N$4,Staff!$A$30:$IN$30)-1,30)=M$5,ROW(INDIRECT("1:30"))),ROW(A1)))))

Confirm as an array formula

In staff sheet use this one

=INDEX($D$31:$IN$51,MATCH($A6,$A$31:$A$51,0),MATCH(1,($G$2=MONTH(DIENOS))*1,0)+D$5-1)

For more info see workbook