The validation of "" failed with error "Not Found" (HTTP code 404)

hi mi question is: when i try add my site says me “The validation of “” failed with error “Not Found” (HTTP code 404).”, but i have try on server start matomo plugin whit curl:

[root@srv-dru01 ~]# curl
This resource is part of Matomo. Keep full control of your data with the leading free and open source web analytics & conversion optimisation platform.

is correct ???
why plugin not function?

i have tried register account of site on matomo cloud and function correct.

my server is:
not good :