I have searched and found a few issues on structure blocks but not one that similar to this.

When trying to save a structure, the corner blocks work fine and when I add the block to save, it detects the structure and puts the bounding box around it. However, when I click Save, the GUI disappears but nothing happens and I don't get a message telling me structure saved as ***

I tried using redstone to see if it would save to memory but this also didn't work

I tried manually creating a folder called structures at the location:
AppData\Roaming\.minecraft\saves\WORLDNAME\generated\minecraft
(This is the location a different world generated in the latest stable release that worked)

However this did not work.

Thanks

Mark