Hi John. Have you assigned the external Drive a drive letter?
May show in Device Manager but Your computer needs to recognize.
We ask you to try different things for a reason, not always immediately understood. It's a process of elimination.
You said you tried the format link I gave you. What did you try?
Try these steps:
Open Command Prompt. (CMD)
Type: diskpart
At the DISKPART prompt, type: list volume
Make note of the number of the simple volume whose drive letter you want to assign, change, or remove.
At the DISKPART prompt, type: select volume n
Select the volume, where n is the volume's number, whose drive letter you want to assign, change, or remove.
At the DISKPART prompt, type one of the following: assign letter=L
Where L is the drive letter you want to assign or change.
You can make L any letter as long as it is not already assigned to a drive.