No protocol specified Unexpected error in Briefcase

I can run functions: pull_remote() and export_data() on Windows. However, when i am trying to run these functions on ubuntu it gives this error :

"No protocol specified
Unexpected error in Briefcase. Please review briefcase.log for more information. For help, post to https://forum.getodk.org/c/support"

I also tried to pull by using ubuntu terminal and it worked perfectly
Terminal code:
"java -jar {path/to/briefcase-jar-file} --pull_aggregate --storage_directory {path/to/briefcase-storage-location} --aggregate_url {aggregate-url} --odk_username {username} --odk_password {password}"

However, same code is not working, when i am using R. It gives same error.
R code:
system("java -jar {path/to/briefcase-jar-file} --pull_aggregate --storage_directory {path/to/briefcase-storage-location} --aggregate_url {aggregate-url} --odk_username {username} --odk_password {password}")

Error:
"No protocol specified
Unexpected error in Briefcase. Please review briefcase.log for more information. For help, post to https://forum.getodk.org/c/support"

What can be the reason ? Can you help me ?