One or more of your email addresses have bounced. Check email addresses status.
Clicking on "Check email addresses status" results in a list of email addresses I've added to LinkedIn, the top line of which reads:
linkedin.xxxxx.xxxxxxx@xoxy.net Primary Address Bounced
So, email from LinkedIn to my xoxy.net address bounced. I assume this is a temporary problem, but I don't know. I worry that email to me from other sites (e.g., my kids' schools) may be bouncing without my knowledge.