I would recommend open case with HCL.
This typically occurs for a few reasons, such as proxy, firewall, AV problems, or corruption.
I’ve seen this problem a lot, but in my situation, it was with compliance sites which was related to some internal DB issue, where it was usually OK to remove and re-add from the console. If that didn’t work, removing it from the database and adding it again from the console was the final fix.
However, in your situation, the issue relates to the BES Support site, which cannot be removed. Therefore, instead of tampering with the system, open a case for a thorough investigation.