If you need support from Yola please contact us via support@yola.com or make use of our live chat service! We are working on a new approach to community-based support and during this transition period we are not adding any new threads to this forum. Many thanks to everyone who has participated over the years and we look forward to unveiling a new peer-to-peer support system soon!
For which domain did you try to change the nameservers? For your domain tjcanvas.co.uk the A records aren't pointing to Yola, but for your other two domains they are.
Please also provide the nameservers and their IP addresses, so that we can try to add them for you.