Update SSL cert on MK1000 - error "cert must have RSA pub key"

Development Tools IDE 1.x
1

Using the FirmwareUdater to upload root certificates on a MK1000 brd and domain arduino.cc:443 .

I get the error msg "SSL certifcate must have an RSA public key".

I am new to this brd. THis is a model B, using firmware 19.4.4. Programmer is working

Any help welcome, did not find much about that error msg online