Mac Pro Mid 2012 Memory Upgrade

First, is this a Retina or a non-Retina 2012 MacBook Pro. Only the non-Retina 2012 MacBook Pros have user-upgradeable RAM.

If a non-Retina, the you bought the wrong RAM. OWC's part number for compatible RAM has the RAM speed embedded, and you bought 1867mhz RAm for a computer that uses 1600mhz RAM

From the OWC RAM page for the Mid 2012 non-Retina MBP:

In the pre-2006 Macs(before Intel processors) most Macs were happy with RAM that was a little too fast. Today you need to match the speed to the spec or you can be knee-deep in stability issues.

Return the RAM you have and get the part number shown above. If you did not buy directly from OWC, do so if at all possible:

https://eshop.macsales.com/item/OWC/1600DDR3S16P/

Check on the OWC site to see what memory is compatible with what computer.