Thank you very much, my friend. I'm downloading it manually for now, but it seems strange to me. Does anyone else have this error with "online package manager"? 
I had this error(Linux Mint).
But it was also the system update manager not working.
The problem was a blocking of port 80.
But it was my own fault, I used bolvan-dpi and set the wrong settings.
This behavior can also be caused by some VPNs.
PS: I have the error on Windows and Ubuntu.
Strange that you have the same error on different systems. I have only one assumption that the blocking is coming from the internet service provider. check if there is a response on port 80
>
telnet package.lazarus-ide.com 80