Couple of things. Could the 12 speed cog be 1/8th instead of 3/16s that your chain is? That would cause a problem.

Second, chains, cogs and chainrings wear out together. The wear pattern is like a jigsaw puzzle and they fit together nicely. Replace one of those three and problems can occur. This is why you tend to replace at least cogs and chain at the same time.

Third it is SRAM not Schram.

Others will chime in with suggestions. Hope you get it figured out.