The recovery server could not be contacted

 Start up from macOS Recovery

Option-⌘-R

Upgrade to the latest macOS compatible with your Mac.

In Disk Utility>View, select Show all Devices, highlight the top left entry.

APFS won't work for Sierra or earlier, Sierra or earlier needs MacOS Extended Journaled. High Sierra won't work for APFS on earlier Macs.

What has often worked for others is to use this Restore Method instead of CMD+r keys...

Option-⌘-R

Upgrade to the latest macOS compatible with your Mac.

Deleted MacIntosh HD and MacIntosh HD - D… - Apple Community

could not create a reboot volume for apfs… - Apple Community

Remote Recovery Fails to install Sierra -… - Apple Community

Messed up Factory Reset on MacBook Pro Mi… - Apple Community

https://discussions.apple.com/thread/254793247?answerId=258936149022#258936149022

https://discussions.apple.com/thread/254872290?answerId=259072534022#259072534022

https://discussions.apple.com/thread/255040953?answerId=259391356022#259391356022

If all else fails...

Use http:// instead of https://

https://www.youtube.com/watch?v=ouNQS36dIBw&t=95s

https://discussions.apple.com/thread/255392065?answerId=260030948022&sortBy=oldest_first#260030948022

https://discussions.apple.com/thread/254871592?answerId=260022113022&sortBy=oldest_first#260022113022

Oh...

Download macOS

Thanks to eRock1…

 So I downloaded the El Capitan .dmg from the Apple website. Apple can sometimes be a bit cryptic in how to do an easy task, so here's how I did it…

https://discussions.apple.com/thread/255439439?answerId=260122925022&sortBy=oldest_first#260122925022

OS X El Capitan

El Capitan downloads as a disk image. On a Mac that is compatible with El Capitan, open the disk image and run the installer within, named InstallMacOSX.pkg. It installs an app named Install OS X El Capitan into your Applications folder. You will create the bootable installer from this app, not from the disk image or .pkg installer.

Use the 'createinstallmedia' command in Terminal

1. Connect the USB flash drive or other volume that you're using for the bootable installer. Make sure that it has at least 12GB of available storage and is formatted as Mac OS Extended.
2. Open Terminal, which is in the Utilities folder of your Applications folder.
3. Type or paste one of the following commands in Terminal. These assume that the installer is still in your Applications folder, and MyVolume is the name of the USB flash drive or other volume you're using. If it has a different name, replace MyVolume in these commands with the name of your volume.
4. El Capitan:

sudo /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume --applicationpath /Applications/Install\ OS\ X\ El\ Capitan.app

1. Press Return after typing the command.
2. When prompted, type your administrator password and press Return again. Terminal doesn't show any characters as you type your password.
3. When prompted, type Y to confirm that you want to erase the volume, then press Return. Terminal shows the progress as the bootable installer is created. 
4. When Terminal says that it's done, the volume will have the same name as the installer you downloaded, such as Install macOS Catalina. You can now quit Terminal and eject the volume.

Create a bootable installer - Apple Support

This fixed it for me, the #3.

https://mrmacintosh.com/how-to-fix-the-recovery-server-could-not-be-contacted-error-high-sierra-recovery-is-still-online-but-broken/

👍