Received invalid data

Hi guys, after a lot of testing I keep reveicing this message in the logs: “Received invalid data”:

https://tinyurl.com/2od95ena

User are actually passed from site A to site B, but they’re not logged in.

From site A I activate all ongoing actions, but roles and metadata. On site B I activated the some for incoming actions. Although in my case the login start from site A, I won’t need to do that biderectionally, but I still checked the same incoming actions for site A and the outgoing for site A.

Site A – https://tinyurl.com/2e8fj9kd

Site B – https://tinyurl.com/2zh7lr53

Now I triple checked all the practices to understand what I could’ve made wrong:

1. Checked and resaved permalinks on both sites
2. Checked typos in the URLs, even in the database
3. Test connections, test passed.
4. Deactivate all other plugins (I have no security plugins installaled)

This is still the message I keep receiving.

Thank you for clarifying