It is hard to tell only from this information. If you are using Nprinting to connect Qlik Sense, then it may captures message “Proxy Authenticate request(ReceiveRequestAsync) failed." which is not harmful.
Do you experience any actual problem when this message occurs? Also you may turn on log level of Proxy to debug and see any clue captured.
If it didn't work before, good starting direction for approaching this is to review the environment setup. Who did set up this environment? Is the person who set up this environment have successful experience on setting up similar environment in the past?
If it worked before, when did the issue start to happen? And any changes to this environment?
.png "Former Employee"){kind=icon}
