2015 MBP won't restart, seems to be preventing updates??

[Beanz!]

I've got a new-to-me 2015 15" MBP. I've transferred all the data from my even older MBP, and am now trying to update it to Mojave (it's currently on El Capitan 10.11.6). It takes the 15 min to download, then it starts to restart, but during the restart it freezes on my blank wallpaper. I'll force a restart with either cntrl+cmmd+power button, or just turn it off then on again, but when it turns back on it's still on El Capitan. I've also tried to update the Software Update from the App Store, and like the Mojave update, it downloaded everything, tried to restart, freezes, and when I come back on and return to the App Store, the "UPDATE" button now reads "RESTART".

It seems that by not "properly" restarting, my laptop is unable to update?? Any thoughts?

UPDATE: I tried restarting from the Login Screen, you know, where you type in your password and below are three buttons: Sleep, Restart, and Shut Down? I clicked Restart and from there I got a "proper" restart and my apps updated. However, this method doesn't seem to do anything for updating to Mojave. PROBLEM STILL UNSOLVED.

 

[Fishrrman]

I'll try to help.

In a situation like this, if it was me, I'd advise this:
1. BACK UP your current internal drive to an external drive.
I would STRONGLY SUGGEST that you use either CarbonCopyCloner or SuperDuper to do this. Both are FREE to download and use for 30 days.
2. Download a copy of Mojave (more on this below).
3. Create a bootable USB flashdrive installer. (you will need a 16gb USB3 flashdrive, or larger).
4. Boot the MBP from the flashdrive
5. ERASE the internal drive to APFS
6. Install a fresh copy of Mojave
7. RESTORE your data during the initial setup process using the cloned backup and setup assistant.

Where to get Mojave?
Go to this page:

macOS Mojave Patcher

dosdude1.com

Download the "Mojave Patcher" utility
Launch Mojave Patcher
DISMISS any alert that says "supported/unsupported".
Now... go to the "tools" menu and you have a choice to download the Mojave installer -- DO IT.
Once you have the installer on your drive, use one of these free utilities to create the bootable flashdrive:
Diskmaker X (be sure to download the correct version for Mojave)
or
Install Disk Creator.
Either one can create a bootable flashdrive using only a few clicks of the mouse.

Then use the flashdrive to boot and install, as above.

YES, this is a good amount of work.
But I'll predict that following it carefully WILL "get you to the goal" you are trying to reach.

Good luck.

 

[startergo]

and am now trying to update it to Mojave (it's currently on El Capitan 10.11.6).

Hmm, Not sure what firmware you still have, but you can update the firmware first and try again.
InstallAssistant.pkg
Run the installer to extract the application to the Applications folder

• Mount Monterey SharedSupport disk image:

/usr/bin/hdiutil mount /Applications/Install\ macOS\ Monterey*.app/Contents/SharedSupport/SharedSupport.dmg

• Store ZIP file path to variable (handle unpredictable file name):

ZIP_FILE=`ls /Volumes/Shared\ Support/com_apple_MobileAsset_MacSoftwareUpdate/*.zip`

• List firmware files in ZIP file:

unzip -l-qq "$ZIP_FILE" "AssetData/boot/EFI/EFIPayloads/*"

• In Terminal.app, first verify your EFI version using the following command:

/usr/libexec/firmwarecheckers/eficheck/eficheck --integrity-check | grep "EFI Version"

• locate the firmware file and store the exact file path into the variable FIRMWARE_FILE:

FIRMWARE_FILE=AssetData/boot/EFI/EFIPayloads/MBP114.scap

• Extract the firmware file ( "-j" means don't create directory structure and "-d" designates that output directory):

unzip -j "$ZIP_FILE" $FIRMWARE_FILE -d ~/Desktop/

• Set your MacBook to upgrade the firmware on the next bootup (SIP must be disabled). Fill in the file name of your specific firmware file:

sudo /usr/sbin/bless -firmware ~/Desktop/MBP114.scap --verbose --recovery

• Trigger firmware upgrade: Shut down your computer. (Do not choose the restart option!) After the MacBook is powered off, power it back on by pressing the power button. Next be patient, and if everything goes well your firmware will be updated.

Try upgrading to Mojave afterwards.


Or you can make it easier for you. Try installing Monterey directly from the first step.