I would wait for the response from their support first
Fairlay has a good reputation and I never had any problems with them
as for the possible reasons it could be the tainted coins you got from an exchange or your IP flagged
it is not like the bookie wants to steal your coins - they got an alert from the security team and then it all goes "we check and do not tell you what it is"
leaving a polite reminder in their topic here and nagging support usually helps more than any confrontation
but if it results in nothing good for  you and your money are held , open a scam accusation topic , but for now I would suggest waiting for a response
sometimes false positives happen , errare humanum est like our Latin friends used to say