Combat doesn't work for me either, I'm on desktop/browser and my character is unable to attack.
Here's everything I did:
Started as a guest -> chose the ninja class -> followed the tutorial -> got to the combat section of the tutorial and after spending a few minutes searching for an attack button, I finally realized my character was just completely unable to fight back due to a bug or whatever -> tried refreshing the page, restarting my browser, re-equipping my weapon and yokai and creating an account but nothing worked
Okay I just figured it out as I was typing this: you can't use the stone axe as a weapon, equipping it makes your character unable to attack and I'm guessing you can't use any other tool for combat either (Chopping a sakura tree also takes longer with the stone axe: stone axe: 3.15s, No tool: 3s)