Check to see if the inserts are too deeply recessed.
If the metal insert isn’t flush with the surface, the screw won’t engage the thread and will instead appear to ‘spin’ around without attaching.
To fix this, take a hex key and “back out” the metal insert using a counter-clockwise motion until it’s flush with the desktop. Repeat with other inserts if necessary. Once they are all level with the desktop, you should be able to attach the frame to the top without issue.
We include a 3mm hex key and a 4mm hex key per desk frame.