Is there a little black dot that jumps around closely following your cursor?
My guess is that you have activated the grid snap.
The keyboard shortcut is by default .... s
Press "s" again and then see if you can select.
Barry.
One of the forum moderators.
Versions 6.5 to 27
i7-10700 @ 2.9Ghz, 32GB ram, GeForce RTX 2060 (6GB), Windows 10
Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11