Adding a rung in online mode control logix

I am still new to control logix, I am trying to add a new rung in the ladder with a new tag in it also can this not be done online.

I have made other changes online but never added a new tag or rung on this plc.

I don't get the accept rung thing to press

it has an older L55 processor in it.

what is the state of the key switch on the processor? Is it in run perhaps?

After you enter the new rung, right click on any of the new tags involved and make tags out of them. The right click menu should offer a line that says "New 'whatever_your_tag_name'"? And if you choose that, and be careful that you pick the right data type, scope, and array size (if applicable).

That should take care of any tag issues. I have heard reports of the verify button getting stuck greyed out for other reasons, but the right click menu (on the left of the rung) should tell you if the rung is ready to be accepted.

What firmware version also?