Refresh Delay for Sign-up Page

We are experiencing a sporadic refresh problem where a user will volunteer for an opportunity, they receive the email, they show as being sign-up in the plug in, but the sign up page does not reflect this sign up. (i.e. the opportunity is still available) I’ve refreshed the browser, I’ve hit it from a different browser and a different device. It ultimately clears, but is a bit frustrating and confounding while it is in the error state. Is there a setting I”m missing, or something that I need to change to get it to refresh faster?