The Promotions are configured with these upstream criterias:

• A: manual
• B: manual, when A is promoted
• C: manual, when B is promoted

1.User Approves promotion A

2.User Clicks on the approve button of Promotion C.

3.User Approves promotion A

On following the above steps promotion C is getting auto promoted after Promotion B is approved.

First of all the approve buttons of downstream promotions should be disabled if one upstream promotion has  not happened and downstream promotion has dependency on it.