When making changes to my calendar I receive this message “There’s a problem connecting to Calendar right now. Please make sure that you’re connected to the Internet and try again.” What can I do?

The changes I make seem to be reaching the website but the signal coming back seems to get lost.  If I make a new appointment and hit save I get the error but if I refresh the page the appointment is there.  In searching for a solution, I have cleared my cache several times and I have tried using different browsers, to no avail. The error also appears when I try going to settings and moving from week to week.