[PS1.7] Can't connect to webservice

[Jurist]

Hello,

We have PS1.7 store and problem with webservice. When we open:

https://mydomain.com/api/

the prompt asks for username and password, we type API KEY generated into the back office into username field, password remaing empty, however nothing happens, the store just asks for those credentials again.

when we try to access:

https://mydomain.com/api?ws_key=MYAPIKEYHERE

we can see a response. 

I tried adding .htaccess to /webservice folder, however it doesn't help.

Store runs PHP 7.3 with cgi interpreter.

How do we fix that? At the moment no API connection to the store is possible.