So, I think I've figured out why some of our members are having trouble seeing other's responses in their notifications. We have a following feature on the site, and you'll have to be following anyone that you want to get notifications from. You can change some of the settings in your account, but if you want to get notifications from anyone on the site you'll need to go to the member's page and follow the other members.
As far as messaging goes, we do have a bit of a hangup with messages going through on the wix app, so you'll most likely have to send them directly on the site. Your messages most likely have a number on it that says you have a message that has been unread, but it is something that wix will have to fix, but don't worry about it for now.
And for visiting other's profiles and your own, there will be an error when you visit profile pages. There have been troubles with getting profiles to load due to problems with the main wix site, but you will have full access to your profile settings through your account.
<3 have a great day.