Linking and syncing seem a bit funky with Alexa. Or is that problem elsewhere?
I previously had linked both any.do and Todoist to Alexa, as I tried both of them out. The problem is that any.do's own syncing is horrendously bad. So I then tried Todoist, which works well. But the lists on Alexa seemed stuck in neverland from a sync standpoint; they would feed fine outbound to Todoist, but Todoist updates were not coming back to Alexa.
The moment I eliminated the any.do link, the sync between Alexa and Todoist worked instantly in both directions.
So I'm not familiar with how your calendar accounts are configured. But you might need to look beyond Alexa for the problem.
EDIT: I just used Roger to test my google calendar sync. I put a new event on for tomorrow, then within five seconds asked Roger (alexa) "What's on my calendar for tomorrow?" And Alexa already knew the event. So clearly, the issue is out there in your calendar accounts somewhere.