Our engineers investigated a problem that was affecting Yammer Embed users that are utilizing IE 8 as their browser.
We were able to identify the Root Cause of this issue as such:
IE8 was returning 304 headers instead of the full document body and was showing empty html it had decided to generate itself. There is a known issue with IE8 intermittently interpreting responses as 304’s, and we think that might be somehow related
The fix that we were able to deploy was to replace the URL which was redirecting a browser to a direct Yammer network specific URL returning a proxy page without any redirects + cache-busting.