Google Material Icons only work in Firefox

Since upgrading to 9.11 I find that Google Material Icons only work in Firefox (see screenshot) and https://lowestoftoldandnow.org/. It worked fine in all browsers in 813. Appreciate your guidance thanks

.frontevents h3::after, .field--type-datetime::before, .field--type-smartdate::before, .views-field.views-field-field-when::before {
  content: "event";
  font-style: normal;
  font-family: 'Material Icons';
  position: relative;
}