In this case, it is likely that Ketryx is blocking approval of the item because an upstream item is uncontrolled.  This is particularly true if the Project Settings are configured to prevent approvals in this situation.  To understand if this is what is happening, you can:

1. Check the item's approval ability by navigating to the item record.  On the right hand side of the item record page, click Details in the upper right hand corner.  A side panel will appear on the right hand side of the page.  If the approval is blocked, a blue box will display a message saying: "Your approval: the approval of this item is blocked."  Underneath, a separate blue box will display another message explaining why, which will include all the upstream items which are unapproved and blocking approval of this particular item.
2. Check whether upstream requirements must be approved.  To do this, navigate to Project Settings.  Under the first heading, Design Verification, you can see whether the box is checked: "Require controlled design inputs before a design output can be approved".  This is a project configuration setting which will explain behavior of Ketryx as it applies to the entire project.

So, in this case, the approval of an item is blocked because Ketryx is functioning as intended.  Upstream requirements must be in a state of control prior to approval of this specific item.