recovery server could not be contacted

Are you using Target Disk Mode?

if you are, (the T key at startup), that makes your hard drive an external hard drive with only the knowledge of the connected computer as to what to install software from. The installer will sensitive to the host's CPU, not the target's CPU. An error of the target could happen in the fashion you describe.

A 2020 MacBook Pro as a host will never allow High Sierra to be installed because the operating system is too old for it.

A 2017 MacBook Pro might allow High Sierra to be installed on a 2009 MacBook Pro set to target, but once booted the 2009 MacBook Pro won't understand what High Sierra is as it is too new for the 2009 MacBook Pro.

Target disk mode may allow High Sierra to be installed on a 2009 MacBook Pro, and boot a 2017 MacBook Pro, but the 2009 MacBook Pro on its own will never support High Sierra.

Any machine with the T key booted is essentially a glorified external hard drive until it tries to boot on its own. Then its CPU will just which OS it is compatible with.

Host machine is the machine linked to the computer that booted with the 'T' key.

Target machine is the machine that booted with the 'T' key.

Hi! I Musa from Tanzania, I got problem with my MacBook pro model A1990 when I recovery via internet then it bring high Sierra which is not compatible with my Macbook and so give me error *The recovery server could not be contacted* I tried to back date of MacBook but unfortunately still bring that error message

That generally is due to some issue with your internet access. Musajr2020, if you can't help the original poster of this thread, please start your new thread by selecting Ask the Community above.

User level:

Level 1

There is no reason to do the flash drive method.

What you need is a good powered USB-ethernet hub such as:

https://www.smklink.com/products/usb-c-multi-port-hub

https://www.siig.com/search/JU-DK0F11-S1

and to plug the power of the laptop directly into the hub and an ethernet cable between the hub and the modem.

That will give you the internet connection necessary to proceed. Chances are it is not conveying the WiFi connection properly to the recovery server. command-option-shift-R at startup loads recovery, and allows you to restore the operating system from Apple directly.

If you have any data on your computer you need to recover, and you can't boot the system with the Option key, take a place that recovers data from Macs. http://www.apple.com/buy should help.

First format Mac OS Extended Journalled if you have no data to perserve. Once formatted Mac OS X Extended Journalled, it can be formatted APFS if the installer is for HIgh Sierra or newer. If it is for Sierra or older, you'll need to upgrade to High Sierra first.

If that's happening, it sounds like your built-in storage is damaged.

I would bring it into a service center to determine the health of the drive, and see if they can help you upgrade.

Generally the flashing question market disk indicates there is no workable system available. If it is appearing in internet recovery mode, and you are certain the internet is there, it has no place to download the recovery partition to that it can write to, which indicates a problem with the storage device.

What Format does Disk Utility say it is?

You select the top most volume belonging the the volume you want to erase using View menu - > Show all devices. Note, this action is not reversible.