Merge Serial Tracked Products Not Working

I am trying to merge two Serial tracked products and I am getting a message to tell me that the Serial tracking settings are different.

Solution

When merging Serial tracked products, the settings on both product need to be exactly the same.  Please go back and check the two products that are being merged.

For example when trying to merge these two product codes

As you can see the Product below does not have the Track Purchased Serial option ticked. 

See here to change the serial tracking on Products