Trouble with Cheap Chinese Chablet - Android Q&A, Help & Troubleshooting

I'm having problems with a Chinese tablet that I believe to be a Mediatek TAB910 with a MTK6592 processor.
It started by having problems with the SIM slots which I put down to a faulty SIM card. I obtained another from the telco but that didn't solve the problem. I concluded that the problem was with the SIM slots or with the software so I did a factory reset.
That appears to have gone well EXCEPT that I cannot get past the "Enter Privacy Protection password" screen (PPP). Let me say at this stage that I have never used PINs on my SIM cards; in fact, if I put a SIM card in which has a PIN then the screen asks for and accepts the SIM PIN but still presents the PPP screen.
I have tried to connect to the tablet by USB in order to try SP FLASH, but that tool doesn't see the tablet at all.
I then tried sudo dmesg|grep usb to see if there was any recognition of the USB and got the following results:
[237820.461318] usb 1-2: new high-speed USB device number 22 using xhci_hcd
[237820.611762] usb 1-2: New USB device found, idVendor=0e8d, idProduct=2000, bcdDevice= 1.00
[237820.611773] usb 1-2: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[237820.611779] usb 1-2: Product: MT65xx Preloader
[237820.611783] usb 1-2: Manufacturer: MediaTek
[237823.266112] usb 1-2: USB disconnect, device number 22
[237830.885144] usb 1-2: new high-speed USB device number 23 using xhci_hcd
[237831.034440] usb 1-2: New USB device found, idVendor=0e8d, idProduct=2002, bcdDevice=ff.ff
[237831.034451] usb 1-2: New USB device strings: Mfr=2, Product=3, SerialNumber=4
[237831.034456] usb 1-2: Product: TAB910
[237831.034461] usb 1-2: Manufacturer: MediaTek
[237831.034465] usb 1-2: SerialNumber: 0123456789ABCDEF
[237831.038098] usb-storage 1-2:1.0: USB Mass Storage device detected
[237831.045186] scsi host2: usb-storage 1-2:1.0
[237831.471860] usb 1-2: USB disconnect, device number 23
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It appears that the tablet is identifying itself, but immediately disconnecting again, hence no response from SP FLASH.
I can get the tablet to drop into two factory setting levels, one with English language instructions, the other with Chinese language instructions. Both of these appear to work as expected when I run through the menu items including, in the Chinese menu, "Eliminate eMMC".
I have also modified the udev files, but seemingly to no avail.
~$ cat /etc/udev/rules.d/80-persistent-usb.rules
SUBSYSTEM==”usb”, ACTION==”add”, ATTR{idVendor}==”0e8d”, ATTR{idProduct}==”2000“
SUBSYSTEM==”usb”, ACTION==”add”, ATTR{idVendor}==”0e8d”, ATTR{idProduct}==”2002“
~$ sudo service udev restart
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My question is: Where do I go from here before I decide to bin this chablet.
TIA

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For your reference.
https://visihow.com/Bypass_Privacy_Protection_Password_on_Android

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James_Watson said:
For your reference.
https://visihow.com/Bypass_Privacy_Protection_Password_on_Android
Click to expand...
Click to collapse
Thanks for that but I have already been down that rabbit hole without success. My big problem is that the USB comes up but promptly disconnects again

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Usually MTk preloader comport will disconnect if correct bootloader is not detected. So check you've got MTK6592 supported sp flashtool version and original firmware loaded. For privacy protection removal you need to format whole flash except bootloader and flash origin firmware then need to repair imei.
For some models you need to press and hold VOL+ or VOL- or both to get in to flash mode.