I am trying to submit an application adding new segments and new pipeline installations to my project, but I cannot add the installations via new spatial or the “Add Installation” button?

If you are adding both new segments to your project and new installations to those new segments, you must ensure that you have submitted the spatial for the new segments before you try to add the associated pipeline installations to them.  All installation points must correspond to the correct (and available) Segment IDs for the amendment or uploading pipeline installations will not work.