Good day

Please check if the address has changed on your IIS, right click on your site then click edit bindings check if the host name reflect the same name as your new address, edit the hostname to match the new one.  if all the mentioned options don't work out please do an IIS reset. 

Should this work please mark it as a solution or give a Kudo,

Thank You

Thabang

Thanks for reply, unfortunately it didn't help. 

Maybe I'm wrong but is it not weird that i can access https://address/management from different machine but cannot do it from server hosting it?

Edit:

There might be some changes in K2 management -> Environment Library is it possible that there is some error?

Hi  @Wojciech

I'd like to give few research links which i believe they gonna help you tacked the issue, please follow up with the following links respectively:-

1. https://community.k2.com/t5/K2-blackpearl-Articles/4*personal details removed*-Unauthorized-access-when-signing-to-K2Workspace-from-a/ta-p/80921?nobounce

2. https://help.k2.com/onlinehelp/k2blackpearl/icg/4.7/default.htm#Prepare/SetPermSA_IIS.htm

3. https://help.k2.com/onlinehelp/k2blackpearl/icg/4.7/default.htm#Prepare/SCC/IIS.htm

Thank you, Please mark this as a kudo or accepted solution if you find information provided helpful.

K2 will not accept any liability for any issues arising from actions taken in respect of the information provided by any forum member.

Hi Wojciech

Under authentication please check if your settings are as follows and let me know:

Anonymous Authentication: Enabled

ASP.NET Impersonation: Disabled

Forms Authentication: Enabled

Windows Authentication: Disabled

Thank You

Thabang

@Widson thanks for advice!

It didn't solve my problem but it helped me find solution. It looks like all I needed to follow method 1 described by microsoft support. My problem could be caused by loopback check security. 

Hope this thread will help someone someday.

Wojtek