Hello Priyankah,
Please might you give more details?
Do your customer cope with this issue with a specific browser on their Linux machines?
Do they test with Windows machines in the same network and is it fine?
Blank page is usually an issue related to network access denied, so either firewall or Adobe Campaign security zones.
As for network details, ask your customer to do a telnet connection to the AC MTA server (port 80) to check physical firewalls, and ask them to do http://<serverMTA>/r/test
Regards
Jean-Serge