This article provides a solution in case of licenses installation issues.
On operational mode, which has the symbol ">", run "request system license add terminal", press enter, paste your license key and press "CTRL+D":
root@junos-device> request system license add terminal
[Type ^D at a new line to end input, enter blank line between each license key]
JUNOSXXXXXXXX xxxxxx xxxxxx xxxxxx xxxxxx xxxxxx xxxxxx
xxxxxx xxxxxx xxxxxx xxxxxx xxxxxx xxxxxx
xxxxxx xxxxxx xxxxxx xxxxxx