Our company also encounters such problem.

All browsers can successfully display company web-site (bfshina.com.ua), but after Opera VPN enabled - it display error with Nginx (we are using Apache) http://bfshina.com.ua/operavpn_fails_on_access.png. Web-server log shows, that query was successfully accepted and data send back to client agent: http://bfshina.com.ua/other_sites_access_log_with_opera_vpn_IP_connect_tries.png.

Thanks for help.

After verification, it seems like our server is not (or does not seem to be) blocking the VPN, as one of the tests i conducted showed that the server received the opera for developper request and sent the data with a 200 code, see log extract here:

107.182.233.175 - - [07/Jun/2017:19:33:30 -0500] "GET /microwave_ovens-the-latest-best_over-range_microwave_ovens HTTP/1.1" 200 13544 "-" "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/59.0.3071.26 Safari/537.36 OPR/46.0.2602.0 (Edition developer)"

Yet, the page failed with the usual error msg (mentioned at the beginning of this thread).

In further tests, I took the actual HTML of the very same page and saved it under a different file name and uploaded it to:
http://www.alphachooser.com/test-mwpage-asis.htm

Again, that's the very very same page, but then it works, even on VPN!

It seems to indicate that:

• it is not the HTML itself that makes it crash, right?
• it does not seem to be my server either, as the error msg comes from nginx, and I'm serving from apache.

And raises the following questions:

• could it be the filename? Yet it looks pretty ordinary: http://www.alphachooser.com/microwave_ovens-the-latest-best_over-range_microwave_ovens
• how is it that the very same page served dynamically from a PHP script fails, yet the very same HTML (obtained from the very same PHP script) succeeds? Is the Opera VPN able to see that it is coming from PHP and doesn't like that? Yet there are millions of PHP websites...
• Is NGINX involved in that VPN? And if NGINX is what handles that VPN, then the msg seems to be from the VPN itself, but then again what does it dislike exactly?
• Finally, could it be the headers? I got the headers of the PHP vs HTML versions from webconf's check header service and they look like this:

PHP (standard) version:

HTTP/1.1 200 OK =>
Date => Thu, 08 Jun 2017 00:53:58 GMT
Server => Apache/2.2.31 (Unix)
X-Powered-By => PHP/5.3.3
Cache-Control => max-age=14400
Content-language => en
Set-Cookie => lint-item=Bosch+HMV8052U%3A%3Amicrowave_ovens%2F%2F%2FSharp+R-1214%3A%3Amicrowave_ovens%2F%2F%2FGE+PVM9215%3A%3Amicrowave_ovens%2F%2F%2FFrigidaire+FGMV175QF%3A%3Amicrowave_ovens%2F%2F%2FSamsung+ME21F707%3A%3Amicrowave_ovens%2F%2F%2FLG+LMV1683ST%3A%3Amicrowave_ovens%2F%2F%2FFrigidaire+FFMV164LS%3A%3Amicrowave_ovens%2F%2F%2FAmana+AMV1150VAS%3A%3Amicrowave_ovens%2F%2F%2FFrigidaire+MWV150KW%3A%3Amicrowave_ovens
X-Content-Type-Options => nosniff
Expires => Thu, 08 Jun 2017 04:53:58 GMT
Vary => Accept-Encoding
Content-Language => en
Connection => close
Content-Type => text/html; charset=UTF-8

STatic HTML test version:
HTTP/1.1 200 OK =>
Date => Thu, 08 Jun 2017 00:55:40 GMT
Server => Apache/2.2.31 (Unix)
X-Content-Type-Options => nosniff
Last-Modified => Thu, 08 Jun 2017 00:40:22 GMT
Accept-Ranges => bytes
Content-Length => 103206
Cache-Control => max-age=14400
Expires => Thu, 08 Jun 2017 04:55:40 GMT
Vary => Accept-Encoding
Content-Language => en
Connection => close
Content-Type => text/html; charset=UTF-8

Could it be some of the differences seen here? I'd really appreciate some help, as this is kinda mind boggling.