Weird issue with Logitech MX master 3, left click button does nothing, happened suddenly.

Ok so I feel like I am losing my mind, I was on Reddit just before, replying to a DM and I went to click the send button and nothing happened, so I tried to minimise the browser, nothing, left button does nothing, I find out after furiously clicking things at random, like you do, my right click button is now my left click button, but not the reverse, so I follow the steps.

1 - Turn off the mouse, reconnect and see, nothing changes.
2 - Reset mouse in logitech options+
3 - Disconnect dongle and reconnect it, nothing.
4 - Restart PC, login, nothing changes.
5 - remove mouse in device manger. re-add in back as generic mouse, nothing changes.
6 - Take break as I am now upset.
7 - Google all possible permutations of 'left click doesn't work'.
7 - Come here to ask a question as I am now frustrated.

I have been using the mouse for a few hours prior to this, no issues.

Any clues, anything I could try, I read one post where the person opened up the mouse and removed the battery and it apparently fixed the issue, but I think I am still under warranty, I'd have to check though.

Everything else on the mouse works fine, scroll, movement, other buttons.

I have tried to use windows and logitech options to switch mouse buttons to no avail.

I have tried all I can think of to do.

I am also posting on r/logitech