Not correct response after payment [#3409289]

Any idea how to fix this problem?

Getting error:

You are receiving this automated message because your server at the address: https://www.XXXXXXX.pl is not providing the correct response to the notifications sent by the system tpay.com for the transaction TR-XXX-XXXXXX.
The correct response should be: TRUE.
However, the response from your server is:
DOCTYPE html lang="pl" dir="ltr" prefix="content: http://purl.org/rss/1.0/modules/content/

--
Drupal 10.2
Commerce_tpay: 8.x-3.0
Commerce: 8.x-2.36