epmp1000 GPS, can't upgrade

I have an epmp 1000 @ 2.3.4 that I wish to get upgraded.  It keeps giving me an error stating that "Error. U-Boot Digital signature check failed."

Can't get past this point....

Hello Andreas,

Could you please contact me at Fedor.trutsko(at)cambiumnetworks(dot)com?
I would be glad to help you with troubleshooting.

Thank you.