Unable to read external hard drive - posting again

I am a newbie- I posted a similar thread but doesn't show. Please forgive me if this is a repeat. However, there is new stuff here.

I have read other postings on tis topic and I have the following to report:

*I am trying to rescue files from a dual partition laptop (Ubunto 20.04 and Windows10) on a laptop with Ubuntu 18.04. The drive is connected to a USB with a device.

* The disk utility shows the correct Model Number size of 1.0 TB and partition as unknown PMBR (not GPT or VFAT) and disk as /dev/sdb

* fdisk -l gives

GPT PMBR size mismatch (1953525167 != 244190645) will be corrected by w(rite).
Disk /dev/sdb: 931.5 GiB, 1000204886016 bytes, 244190646 sectors
Units: sectors of 1 * 4096 = 4096 bytes
Sector size (logical/physical): 4096 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0x3978e90a

Device Boot Start End Sectors Size Id Type
/dev/sdb1 1 1953525167 1953525167 7.3T ee GPT

*sudo blkid /dev/sdb

/dev/sdb: PTTYPE="PMBR"

* sudo mount -t ntfs-3g /dev/sdb /media/MSI
NTFS signature is missing.
Failed to mount '/dev/sdb': Invalid argument
The device '/dev/sdb' doesn't seem to have a valid NTFS.
Maybe the wrong device is used? Or the whole disk instead of a
partition (e.g. /dev/sda, not /dev/sda1)? Or the other way around?

*sudo ntfsfix /dev/sdb
Mounting volume... NTFS signature is missing.
FAILED
Attempting to correct errors... NTFS signature is missing.
FAILED
Failed to startup volume: Invalid argument
NTFS signature is missing.
Trying the alternate boot sector
Unrecoverable error

*dmseg (relevant portion)
[46635.295549] usb 1-1.1: new high-speed USB device number 91 using xhci_hcd
[46635.496609] usb 1-1.1: New USB device found, idVendor=152d, idProduct=2338
[46635.496626] usb 1-1.1: New USB device strings: Mfr=1, Product=2, SerialNumber=5
[46635.496637] usb 1-1.1: Product: USB to ATA/ATAPI bridge
[46635.496646] usb 1-1.1: Manufacturer: JMicron
[46635.496655] usb 1-1.1: SerialNumber: 000000000000
[46635.505286] usb-storage 1-1.1:1.0: USB Mass Storage device detected
[46635.506130] scsi host2: usb-storage 1-1.1:1.0
[46636.520737] scsi 2:0:0:0: Direct-Access ST1000LM 035-1RK172 PQ: 0 ANSI: 2 CCS
[46636.522973] sd 2:0:0:0: Attached scsi generic sg1 type 0
[46636.524987] sd 2:0:0:0: [sdb] 244190646 4096-byte logical blocks: (1.00 TB/932 GiB)
[46636.525366] sd 2:0:0:0: [sdb] Write Protect is off
[46636.525370] sd 2:0:0:0: [sdb] Mode Sense: 28 00 00 00
[46636.525663] sd 2:0:0:0: [sdb] No Caching mode page found
[46636.525670] sd 2:0:0:0: [sdb] Assuming drive cache: write through
[46636.626289] sd 2:0:0:0: [sdb] Attached SCSI disk

* sudo gdisk /dev/sdb
GPT fdisk (gdisk) version 1.0.3

Partition table scan:
MBR: protective
BSD: not present
APM: not present
GPT: not present

Creating new GPT entries.

command : p

Disk /dev/sdb: 244190646 sectors, 931.5 GiB
Model: 035-1RK172
Sector size (logical/physical): 4096/4096 bytes
Disk identifier (GUID): 54745E9C-107B-4742-95A5-7D51AE90D390
Partition table holds up to 128 entries
Main partition table begins at sector 2 and ends at sector 5
First usable sector is 6, last usable sector is 244190640
Partitions will be aligned on 256-sector boundaries
Total free space is 244190635 sectors (931.5 GiB)

*By installing testdisk and running it I get EFI-GPT partition not available or corrupt. But I was able to recover the MSData (Windows) files, not sure if all of them were seen.

Is the volume really corrupt or do I just need to do something else?

Thanks