I’ve just started experiencing problems trying to delete the last few days archived alert clips from the notification list screen of the iSO app 1.4.48 using either my iPad 3 (iOS 9.3.5) or iPhone 5 (iOS 10.3.3). Last time I cleared the queue was 3-4 days ago and I didn’t experience the problem so I suspect it is likely due to recent changes on the server-side.
Edit > Select All will highlight the all the bullet button on the clips but clicking DELETE and replying to the pop-up “Delete?” confirmation window just removes the bullet buttons, but not the clips. The “Edit / Cancel” prompt at the upper left part of the screen continues to say “Cancel” rather than reverting back to say “Edit” as it normally would after a delete.
After repeated unsuccessful tries on the iPad (which is deprecated by Apple to iOS 9.3.5) I was finally able to get the the archived clips deleted and had more success doing in on the iPhone 5 with 10.3.3 but it still took repeated tries.