This is because Poland, as of now isn’t supported for verification. Brave has stopped supporting many regions because of rules & regulations for every region. Brave is working to get most workable regions up for verification back by the end of the year.
You can also get more updates about regional changes →
PSA - Unsupported Regions
Do note →
You will still be getting BATs until Poland has active ad campaigns for Brave rewards. Those BATs will be given to you in your Brave rewards wallet which you have to claim each month. The only difference is that you can’t withdraw those BATs out of the Brave browser till you connect to Uphold / Gemini.