502. 3 error after upgrade to 21.01

Good day,
We have a server still on an old versions 20.12.i wanted to get it up to date with the latest version but first do an upgrade to 21.01 before moving to 21.06
I upgraded the survey solutions server from 20.12 to 21.01

after the upgrade I received a 502.3 bad gateway error.
this is what is displayed under the detailed error information:
IIS 8.5 Detailed Error - 502.3 - Bad Gateway

I did access the landing page just before the upgrade on the old version.
Have anyone experienced this

Dear @daniedk,

try to access the site directly from the server (via localhost:9700) to see if it is responding.

Best, Sergiy

Dear @Sergiy
Thank you for the reply,
when I use the http://localhost:9700/ I get a HTTP 400 bad request error website can not be found.
I made sure in iis that the site is running

Regards
Danie

Looks like the proxy or whatever you are using in front of Survey Solutions is not lying. It tries to pass the request to the server and the server fails with 400, correspondingly the proxy returns 502.

I am confused with the 400 error message, however. Are you getting plain “400 bad request”? or “Website not found”? Or a combination of the two? What does the screenshot look like? Does it come from IIS? If it does, there must be some additional info there, like it can be seen here:
https://www.thebestcsharpprogrammerintheworld.com/2015/01/19/application-request-routing-arr-self-referencing-itself-400-or-502-3/

Check the Survey Solutions log files. Does it get started at all? If it fails what is the error message?

Hi Sergiy
It seems to be a combination

the log file seems fine, would you like me to email it for you to have a look at it