I would try changing the server address.
In Reference Manager please try the following go to Tools > Internet Search > click on Hosts next to PubMed > click on configure hosts > click on properties > change server address to http://www.ncbi.nlm.nih.gov not http://eutils.ncbi.nlm.nih.gov
I would then try your search of PubMed again.
Let us know if you have any questions or if this does not resolve the issue.