As vineelaregonda said, ensure that you license manager is running.
If it's from a centralized license server, verify that the $SYBASE/SYSAM-1_0/licenses/license.dat file includes the correct info :
SERVER <license_server_ip_or_hostname> ANY 29722
VENDOR SYBASE /<SYBASE_install_path>/SYSAM-1_0/bin/SYBASE
If the license file and it's entries are only for the machine where it's installed and you do not want to run a centralized licence server, you can remove or comment out the lines starting with "SERVER" and "USE_SERVER".
Alse verify that your SYBASE, SYBASE_SYSAM, and LM_LICENSE_FILE environment variables are correctly set AND exported.
Ensure this is the case by logging in as the sybase user, and then checking if they remain if you start a new shell e.g.:
$ksh -o vi<enter>
If exported properly, they should all return the same values as is set in the user's original shell. If not, make sure you export them properly in .profile or wherever they are set.
Bear in mind that for 12.5 SYBASE_SYSAM should usually be set to "SYSAM-1_0", and that LM_LICENSE_FILE typically is set to "$SYBASE/$SYBASE_SYSAM/licenses/license.dat".