To know if it is there but not working, try get someone like a friend register, even if possible that you will be the one that will fund the account with small amount of money.
And alternatively if that may be stressful, note that gambling sites that provides referrers offers to their players do usually have dashboard where you can impute your referrers link and then have all your referral members who registered on the platform following your link on track of their activities and then, you will determine if they are active or inactive based on their recent events of playing.
Note: getting to have your referrals activities on track does not mean you have access to their Privacies but just activity events just as it is in the forum here.
I think some platform may opt out of the referral support if they have acquired a targeted number of players or when their bankroll can not afford the price of the referrers anymore.