Summary
You are using IWSVA and LDAP server. IWSVA requires TeamViewer client with proxy authentication. However, even after providing the proxy credentials, you still cannot use TeamViewer.
Details
Since the customer configured LDAP authentication in IWSVA, all users need to send authentication packets to IWSVA. If the user is using browsers like Mozilla Firefox or Internet Explorer, authentication packets should be sent to IWSVA correctly. When you check the TeamViewer packets sent to IWSVA, they are incorrect. The issue is due to a TeamViewer bug.
As a workaround, open port 5938 TCP on the outgoing side for TeamViewer communication. In this case, traffic will not pass through IWSVA. For more information, refer to this article: Which ports are used by TeamViewer?
If the issue persists, contact Trend Micro Technical Support.