[admin@MikroTik] > /certificate add name=CA common-name=CA key-size=2048 days-valid=3650 key-usage=key-cert-sign,crl-sign
[admin@MikroTik] > /certificate sign CA ca-crl-host=127.0.0.1
progress: done

[admin@MikroTik] > /certificate add name=https common-name=https key-size=2048 days-valid=3650
[admin@MikroTik] > /certificate sign https ca=CA
input does not match any value of ca <<<<<<<<<<<<<<<<<<<<<<<< THIS LINE IS THE ERROR
[admin@MikroTik] > certificate pri
Flags: T - TRUSTED
Columns: NAME, COMMON-NAME, FINGERPRINT
# NAME COMMON-NAME FINGERPRINT
0 T DigiCertGlobalRootCA.crt.pem_0 DigiCert Global Root CA 4348a0e9444c78cb265e058d5e8944b4d84f9662bd26db257f8934a443c70161
1 CA CA
2 https https

i "copy and paste" on a Mikrotik cAP ac v6.48.4 without any problems.

Reset the cAP ac and updated to 7.1rc5
got the same Error!

Having the same issue on rb5009ug with v7.1rc5. I didn't write down what 7.X version it shipped with but it was working prior to upgrade to v7.1rc5