I remember what my issue was. It was this amp, & i too was getting no reply after £500 sent (price was almost too good leading my mind to scream SCAM after no comms from seller like you). So got onto the rep.. & led me through cancelling/ refund/ very swiftly.
As it happens he relisted it, gained my trust ( as had Reverb's system now too) via some comms with each other... & I proceeded to buy it again. 3 days later UPS dumped it upside down, slam onto the road in front of me, before I could say b b but!! Thanks to MusicMan mfr.. not a scratch on it. Relief.