action is not activated error

Hello, i am trying to sync users between 2 sites:

1. https://www.mysite.sk/
2. https://shop.mysite.sk/

I have installed plugin on both of them and have set everything. When I test connection on https://shop.mysite.sk/, everything is ok (green). When I test it on https://www.mysite.sk/, it doesnt work and there is a error message: “Login” action is not activated on https://shop.mysite.sk/ with remote IP 37.9.175.187 (incoming).
This message appears for every action (login, logout, create,…).
The problem is that the IP address in error message is IP address of https://www.mysite.sk/, not the subdomain.

When I tried to connect another site with https://www.mysite.sk/, there was also error message, in which was the same IP adress (so maybe problem is somewhere in https://www.mysite.sk/ ??)

i have tried and checked everything, but i am not able to find out where is the problem. The main page https://www.mysite.sk/ has two DNS A records (one is for mysite.sk and another for https://www.mysite.sk – both have same IP address), can be this a problem? If yes, please can you give me some advices how to figure it out? (when i delete DNS for mysite.sk, there is a problem with page loading).

I am already desperate, i dont want to give it up, because i really like this plugin, it is very effective and simple ??

thanks a lot for your help,

Veronika