I still don't know what the problem is but I built a web page to capture the HTTP header and here is what I found. The only difference I see is that in Excel, the cookies are not sent. They are sent in the browser and also in Word. The cookie is not something I configured myself and may be part of my web host's default environment to support visitor statistics.
The only possibility I can think of is that discogs.com also has cookies and if you send a header without the cookies it won't accept it. Since this is the only site where you have this problem, I would contact them for tech support and ask if they require cookies in the header.
Excel using Chrome as the default browser:
Host: [redacted].com
Connection: keep-alive
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/89.0.4389.128 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.9
Content-Length: 0
Directly in Chrome:
Host: [redacted].com
Connection: keep-alive
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/89.0.4389.128 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.9
Cookie: _tccl_visitor=24e2b377-5391-4465-b87d-079605606a05; _tccl_visit=24e2b377-5391-4465-b87d-079605606a05
Content-Length: 0
Excel using Edge as the default browser:
Host: [redacted].com
Connection: keep-alive
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/90.0.4430.72 Safari/537.36 Edg/90.0.818.39
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.9
Content-Length: 0
Directly in Edge:
Host: [redacted].com
Connection: keep-alive
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/90.0.4430.72 Safari/537.36 Edg/90.0.818.39
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.9
Cookie: _tccl_visitor=24e2b3a8-4050-4b6b-81a4-03632411aa59; _tccl_visit=24e2b3a8-4050-4b6b-81a4-03632411aa59
Content-Length: 0
Microsoft Word using Chrome as the default browser:
Host:
www.[redacted].com
Connection: keep-alive
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/89.0.4389.128 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.9
Cookie: _tccl_visitor=23c75b05-4955-44cf-888f-021557070fe8; PHPSESSID=b48ef90014554bd0ed02e2dccc191ef7
Content-Length: 0
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