Try claiming through your credit card company. If that doesn't work try the small claims court in the Isle of Man.
https://www.courts.im court-procedures claims small-claims-procedure

Ticketgum are scammers and committing offenses under the consumer protection act 1970.

As attached their home page website states:
"Satisfaction Guarantee" - "100% Money back Guarantee"

Yet if you check their terms and conditions small print - they offer "No refund, exchange or cancellation - once you confirm your order - ie hit pay"

This is false advertising and illegal under the laws of the country they operate in and are registered in.