I upgraded to 2.7.5c and the "Register" button in my articles no longer appears. i had been calling the button with the following code;
{dtregister}7{/dtregister}
This would call the "Register" button and direct it to Event 7. With the upgrade, the button is no longer being called and the code is showing up in the front end, not the button.
1) Did you upgrade the EventLink plugin? You can't use the old plugin with the newer 2.7.x component. Same with the modules too.
2) If the plugin is updated and enabled, the only other reason why a Register button wouldn't appear would be because registration is not open for the event.