Fix Bot Detection Issue in registration

The system gets a "Bot detected" error when registering an account on Gradient Network at the step of sending email for confirmation (STEP 4). Registration through Firebase passes successfully, but when attempting to send confirmation email through Gradient Network API, the system detects a bot. Although the captcha is solved and accepted correctly as solved. Through AdsPower with manual solving, the same error occurs, meaning the problem is not in the captcha but in detection at some stage or by some unknown method to me.
GOAL
Find and fix the cause of bot detection so the system can successfully send confirmation emails after registration through Firebase.
ANALYSIS OF CURRENT SITUATION
Successful steps:
STEP 1: Email verification - 200 OK
STEP 2: Referral code verification - skipped (not using)
STEP 3: Registration through Firebase - 200 OK
Problematic step:
STEP 4: Sending confirmation email - 400 Bot detected (sends, writes code 200 OK that API request was received, but bot detected and email is not sent
Headers are correct (seemingly)
Same problem occurs with direct registration through AdsPower
When registering through my own browser everything works fine, even in incognito mode
The script is needed for working with my personal account, not for mass registration, with compliance to all Gradient Network rules