Steam has released a new dedicated server update which fixes the HLTV issue. Here's the quote from the news post:
An update has just been released which fixes HLTV. (HLTV is the proxy server which enables server admins to let large numbers of people spectate games in progress.) When admins restart their dedicated servers, this update will take effect automatically.
In the server browser, try using the "Spectate" tab to find HLTV servers.
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