Specify a Vary: Accept-Encoding header

When I moved host I did a GT Metrix speed test and received this response:

Specify a Vary: Accept-Encoding header

The site is run through both Cloudflare and MaxCDN. For the last two weeks, we have all been back and forth testing and changes settings.

Today I disabled all plugins to wittle things down. When W3 Total Cache plugin is deactivated – the Specify a Vary: Accept-Encoding header recommendation disappeared.

Thinking it may be pulling in a setting from the Cloudflare extension, I disabled that. And the problem still persisted. So now I am pretty sure there’s something in W3 that’s causing this red alert in GT Metrix.

I tried disabling several options that did not make a difference.

MaxCDN is trying to say the problem is resolved as it’s a false negative – but I do not believe that is the case.

Any ideas? I am pulling my hair out.

Thanks in advance for your time.

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