Hi Dolly.lo,
I received the same error message. See details on how to fix.

Do you really need shared number sequence? If not, create a number sequence that's not shared and select that instead of ARG-PR (Or remove ARG-PR, delete and create new). Then select the number sequence again and this error message won't be there.
If you don't remove it from shared, there is difference in how your vendor account number will work. On vendor page, when you try to create a new vendor, the vendor number will be greyed out. You have to select vendor group first and then enter name and when you save, it will generate a vendor number.
However if you do change to regular number sequence like below, then you will not have to first select vendor group.

Give it a try and let us know if you have any further questions.