Travelcheck - con artists!

Do not ever use Travelcheck for booking of flights. They are ************. I booked a flight just before covid hit (2020 ) and my flight to the U K was cancelled. I opted for a voucher that I would use later. When I tried now in March 2022 to rebook a flight to the UK using the voucher it comes up " invalid " every time I try. Contacted Travelcheck by email, they don't have a phone number, and sent a screen shot of the invalid voucher. They said they will reactivate? the voucher but still every time I try and book it still comes up invalid voucher. They have now stopped answering my mails. I see plenty of people have had the same problems with Travelcheck. Don't use them - CON ARTISTS !