Place Label - "Enable to create relative association to elements" is greyed out

Hi Everyone, 

I  was trying to create a label that automatically updates displayed value when associated with  an element that has attached Item Type. 

When I create element in new model and select Place Label, the function "Enable to create relative association to elements" is active. When the element is created in existing model (created by others) this function is greyed out. 

Does anybody know why it is greyed out and how this can be enabled?

Below is a screenshot taken from the existing model.

I am currently using MicroStation Connect Edition Update 16 Version 10.16.01.56

Thanks in advance for your help. 

Best regards, 

Jacek Soroko