Array Formula Problem

[bdav1216]

See the attached spreadsheet -

This formula is in Column C - When the Order Number (Column A) is the same, column C should output the total number of jobs (Column B) for that order.
=SUM(IFERROR((1/COUNTIFS($A$2:$A$25,$A$2:$A$25,$B$2:$B$25,$B$2:$B$25,$A$2:$A$25,$A2)),0))

Currently, my formula is within an array formula - my sample spreadsheet is working fine, but when I use this formula in a larger spreadsheet (with approximately 4000 rows and 60 columns), this formula is grinding to a halt and and my spreadsheet isn't working any longer.

Question - How can this formula be modified to work within my larger spreadsheet?

Can this be done without an Array?

Thank You