Correct an email but not change it….please help

In my account profile I noticed that my email has a capital letter in it. I apparently made a typing mistake when I signed up. When I went online to correct it, because it’s not a new email address, just a correction, the system wouldn’t allow the change. Do the cases matter? Maybe they don’t but I want to make sure everything is set up correctly to avoid further problems.

I’m asking because when I tried to set up a meeting yesterday the invitees did not get the notification. Is there a connection? 

I struggle with technology so any help would be appreciated.

PS I tried calling customer support but the system asked for information that I don’t know where to find and was not able to connect with a rep.