First check the related number sequence(s).

Go directly to the Parameters form in the related module and directly select the number sequence to the transaction reference.

Find the next number in the number sequence, and write it down. It was 501 in my case.

It is not so easy to see the last (largest) sequence number that exists in the actual locations table. There does not appear to be a form that lists all records, as it is possible with the Global Address Book Party list screen.

First find the true name of the location table. Due to the error messages shown earlier, I know the problem was on the address location. So I navigated over to any address record to find the table name.

Right click > Personalize >. Personalize this form > Manage.

Note you will need System Admin rights to see this information.

Use the D365 Table Browser to get to the LogisticsLocation table.

Sorting in Descending order on the Location ID field shows that the next number sequence for the LocationID is far greater than 501.

Go back to the number sequence and reconfigure the “Next” number in the sequence to be at least 1 unit larger than the largest number found in the location table.
I.e. 000003802 ±1 = 3803

After taking these steps I was finally able to create a new vendor.