Server state differs from client

I would refresh the game if it were me. If that doesn't work, perhaps try a different browser.

thanks, already tried both.

Hello,

If you try to attack/move something that doesn't exist, will may see a "Server state differs from client" message.

This is because the server state differed from the client (aka the map is different to what actually is there).

Zooming out, a partial refresh, or a full reload should all fix this issue including browser restart or even using another browser should all fix this issue.

All the best

Maybe you attacked a unit that was spied on before but it doesn't exist now.