You have to check the EXACT lenght of the bar (You may use measure tool and check the schema bar). The schema value is rounded according to yours global settings. If aren't the same you can't merge them (Maybe you see the same label of lenght but there are 2 differnt value with the same rounded value).

You can't also have the same mark number (even if the exact lengh and shape is the same) if bars are at diiferent layer.

Hello,

First, please clarify which tool you use, for example Bar shape and select the form or do you use area reinforcement.

Than in a second time, if you have use allready the tool "Rearrange Mark Position" and you have click on "Lock", the position will not be merge.

Bye & Good Use!