Could not connect to appstore: cURL error 28: Operation timed out after 10000 millisec

Nextcloud 18.04
the list of applications is empty.
Errors in log:
Warning appstoreFetcher Could not connect to appstore: cURL error 28: Operation timed out after 10000 milliseconds with 306688 out of 5055472 bytes received (see http://curl.haxx.se/libcurl/c/libcurl-errors.html)

did you search the forum? Like this:
https://help.nextcloud.com/search?q=cURL%20error%2028