Help any idea why my standoff screws are not bitting into the post

Hi got my components for my long over due upgrade which I nerd to do as my old rig isn't tpm2 so windows11 is not going to work.

After a bit of struggling with the ram and cpu cooler. The board is all prepared and ready for install into my old case. I removed the old mobo fine lined the IO up and the standoff holes look right. However I can't feel the screws tightening when putting them in and often they are coming back up on yh magnetic screw head.

The only thing I can think of is somehow my screws are to short as I'm just replacing the previous screws to the new board. My new board does have a backplate covering all the pointy pins on the backside. Which I liked whilst moving the board around but wondering if this is preventing them reaching the standoff posts. Any idea what I need to do