Can't install High Sierra, and other problems

[LexMxyzptlk]

My 2011 iMac running the latest version of Sierra before High Sierra started acting up: slowing to a crawl, beachballing, very low quality video streaming. I tried reinstalling the OS but internet recovery didn't work – the log showed error messages about the connection being "invalidated."

I took it to the Apple store and they reinstalled the OS, tested the hardware etc. and said everything checked out. Got it home and the same problems started up again. Then I took it to a local authorized repair shop and had them put in a new SSD. But they restored from Time Machine which must have contained whatever caused the problem in the first place as it started all over again.

Since then I've been trying to erase the disk and install the OS from scratch, thinking I'd then just transfer my files from iCloud. But internet recovery still will not work. I tried making a bootable USB drive, and it did, once, allow me to wipe the disk and install High Sierra. But all sorts of other things went wrong. For instance, in Mail, when you click on Preferences, nothing happens – no window at all. I looked in Library and there's no mail plist, so it's impossible to make a new one by removing the current one. When I try to reinstall from the USB drive, it freezes, or won't connect to the mouse, or creates some other problem.

The internet recovery can't be a wireless problem, because I tried it on another computer in the house and it worked fine.

Thoughts?

 

[jerwin]

One of those internet speedtests e.g this one may give you an extra datapoint. Compare with your other computer.

 

[cruisin]

A wild shot: is your time reasonably accurate? Secure connections (like internet recovery and Mail) need the correct time to work. See your time accuracy: https://time.is

I would install a fresh copy, see if the problem reoccurs, and if it does go back to the Apple store and let them see the issue. Because if the software is fresh then it means that the hardware is having occasional glitches (the fun kind where it is impossible to show).

 

[Fishrrman]

If you have an SSD inside, it should be running "fast enough".

Do you have a copy of the LOW Sierra installer?
Can you make a USB flashdrive version of it?
If so, boot from that, then ERASE the internal SSD and make sure it's set for HFS+ with journaling enabled.
Then... try a Low Sierra install.

You SHOULD NOT rely on "the cloud" for your important document storage.
Rather, get an external drive and use either CarbonCopyCloner or SuperDuper to create a bootable cloned backup of the internal drive.

Then... if you're having any kinds of problems with the internal (as you are RIGHT NOW), it's trivial to connect the backup and boot up from it.

 

[LexMxyzptlk]

One of those internet speedtests e.g this one may give you an extra datapoint. Compare with your other computer.

Problem solved! I don't know why I didn't think of this. For some reason the download speed was almost zero on this device only. I'm not sure how I did it but a few tweaks of the router and all was well. Many thanks!