this happened to me recently. what i did was go MANUALLY download the 1.3.1 firmware directly from the site.
Before I did this, it would try to upgrade but fail, endlessly. It prompts you to "upgrade" and you can then choose your manually downloaded firmware. This failed a couple times. It kept disconnecting at 10%, !4%, 20%, etc and maybe this is superstitious, but on my successful attempt I also held down both octave up and down keys.
it's fixed, regardless. whoosh. thought i bricked my keystep!