I suppose you are asking me :) Desktop, macOS / Chrome, login with extension.

The button shows up after some minutes but is disabled.

Sometimes I'm not able to paint neither, after I click "Place" the contdown starts but the coloured dot is not placed on the canvas.

It happens to me sometimes, the pixel does not appears until a relays return it back, so it there is bugs it appears to be related with latency. I'll check it out thanks! About the zaps, what's the extension?