Recalibrate your scale with a check weight.
When you turn it on, it zeros to whatever is on the platen. Anything less than that weight will read " - E ". Doing a cal with an empty platen then just the check weight will reset your zero point to just the platen weight, then you would be able to put the cup on and zero as normal.
...or if that fails, unplug it, wait 30s, then plug it back in and turn it on again without the cup on the platen. A Sikorski reset works 60% of the time, every time.