BBS Web app Admin internal links redirect back to login page

Hi, I am having an issue with the Administrator login for my TetraBBS portal. After successfully logging with Admin privileges at: however, the internal links are redirecting back to the login page. For example, there is a link to messages posted, and if I hover on it, it points to:

Right before the issue, the disk space was at 97% capacity of 60GB. To resolve the issue an extra disk space of 60GB was added. Error log file which was at 37 GB was deleted from the server and backed up on personal computer. There is plenty of free disk space now. However the problem still persists. Here are the cPanel and WHM version details:

• cpanel_and_whm: 11.76.0.22
• operating_system_name: centos
• operating_system_version: '6.10'

Any help to resolve this issue will be greatly appreciated.