NTP configuration on HP switch mal-function. NTP requests fail

System:

HPE OfficeConnect Switch 1820 24G J9980A, Firmware: PT.02.12 (May 2021), OS: Linux 3.6.5, U-Boot 2012.10-00116 (Jul 30 2014 - 10:52:01)

The switch connects to ASUS router AC87U.

Setup Network \ System Time \ Time Configuration: (Google NTP service: 216.239.35.0)

Log Error:

"Failed to send 48 byte message to 216.239.35.0 on socket with fd 27. Error 101 (Network is unreachable)."

Extra info.:

When I try to ping that IP from the switch I get the same result (I ping that IP from my Windows 11 Workstation successfully).

-- What else it can be?

Thank you @Silbee

Now I learned that if the 'Protocol Type' selection is 'Static', I have to specify the IP address of the default gateway. If the 'Protocol Type' selection is 'DHCP', the default 'Gateway Address' dynamically acquired (if any).

That was the root of the problem: I changed the 'Protocol Type' from 'DHCP' to 'Static' but did not enter the 'Gateway Address'.

To solve the problem: I restored the Switch 'Protocol Type' to 'DHCP'. With 'DHCP' 'Protocol Type'(*) the Switch dynamically acquired the 'Default Gateway' address.

--

(*) At the Router I manually assigned an IP to the Switch, around the DHCP list.