If you look in your logs, you should find an error message with more details of what error has occurred.
If this doesn't help, you can share the error here and we can try to help.
Hello Mohammad Shamim,
Are you using VPN or in a protected network, if your organisation blocks the request then you might have to configure the Certificates in the Settings -> Certificates tab and add your certificate (either by generating one or by using your company's one)
Hope this helps!