enable https on Dell Networking N1548P

I am trying to enable https and disable http to make dell more secure. I am trying to generate self-sign certificate with these commands and having this error.

(config)#crypto certificate 1 generate(config-crypto-cert)#exitCertificate generation failed. Please check logs for more details..#show loggingSSLT[emWeb]: sslt_api.c(1201) 607965 %% SSLT: ssltCertificateGenerate keyFile not exist