Getting an error while installing a theme or a plugin

I’ve fresh installation of wordpress and I’m getting an error when I add new theme or plugin. Although the site is working properly but whenever I try to add new theme or new plugin it shows an error i.e.:

“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.“

Please try fixing this error I’m not able to add new theme on my local site. And also on Site Health it’s showing:

“Your site is unable to reach www.remarpro.com at 198.143.164.251, and returned the error: cURL error 28: Resolving timed out after 10003 milliseconds“