The button to book tickets on the FixFest page doesn’t show in Safari on High Sierra. When refreshing/loading the page, as the background fades from some cream colour to white, one can briefly see the disappearing link in white. Once the background is white, it’s white on white and it is not visible. The surrounding black rounded button doesn’t show.
Black buttons can work, see for instance these on the same page:
Ideally you’ll fix this issue, but as a fail safe, you may want to consider having the text of the link in say orange, or have the text black and the button grey; i.e., that if the button doesn’t show, at least the link remains readable as not the same colour as the (white) background.