PRIFWPROD01/pri/act# << - this show your FW configure Active/Standby and this ASA is active.
if your FW configured "prompt hostname priority state" you get that prompt based on the what FW you logged in
PRIFWPROD01# ( here you can type show context it will give you contexts available in the FW)
if you are system context or root ( you should be able to issue the command you looking)
also intersted to see what is the error you getting while issueing that command