Hey Nina,
I suggest you should join Slack in Mendix Workspace,
There you’ll find so many amazing people,
https://join.slack.com/t/mendixcommunity/shared_invite/zt-1jpgwqfw1-1dQpkDF0RAowbXhmp907mA
Here’s the link for the slack invite, I also sent this link in the response that I sent to you for your mail.
Hope it helps!
Do you mean on your Mendix profile? I believe there's currently no notifications for these invitations, so it's no wonder that people are not accepting. Are you connecting with a specific reason?