Error on "Add Plugins" page

After I update my websites to 4.0 version, I have the following problem, when I try to search for a new plugin on Add Plugins page:

An unexpected error occurred. Something may be wrong with www.remarpro.com or this server’s configuration. If you continue to have problems, please try the support forums.

I try on different website with different server configuration. Can you help me please to solve this out?

Thanks,
Gabriel M.