Changing a P/N to be serialized after transacting against it

Hi Everyone,

we are running AX 2012 ( r1) and we have run in to an issue. During the set up stage, we thought we had correctly set up all the parts numbers that we would require to be serialization in the future, but when we tried to change the Tracking Dimension Group value it’s greyed out.

Under the Manage Inventory Heading in the PIM, we can change this value to Serialized but the Tracking Dimension Group is Greyed out.

We have about 100 parts that need to be serialized. Can you tell me what my options are?