UNIX account with your name may not have permission to set crontab entries.

Following is transcript from manual pages of crontab. you could check /etc/cron.d/cron.allow or /etc/cron.d/cron.deny files

Users: Access to crontab is allowed:

o if the user's name appears in /etc/cron.d/cron.allow.

o if /etc/cron.d/cron.allow does not exist and the user's
name is not in /etc/cron.d/cron.deny.

Users: Access to crontab is denied:

o if /etc/cron.d/cron.allow exists and the user's name is
not in it.

o if /etc/cron.d/cron.allow does not exist and user's
name is in /etc/cron.d/cron.deny.

o if neither file exists, only a user with the
solaris.jobs.user authorization is allowed to submit a
job.

o if BSM audit is enabled, the user's shell is not
audited and the user is not the crontab owner. This can
occur if the user logs in by way of a program, such as
some versions of SSH, which does not set audit parame-
ters.

The rules for allow and deny apply to root only if the
allow/deny files exist.