Serial Number says it is not valid for our site license

I need someone to actually help us. We may not have the serial number from 2-3 years back of CSS5.5 master collection and I need to get it installed again on 60 brand new pcs that are being replaced. The installer comes up and says that it is not valid.

HELP!!!!!!!!!!!!!!!!!

We paid too much money for this thing to not be active anymore.

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Thanks