This error may occur if the selected bucket region is disabled in your Amazon S3 account.
To resolve the issue, enable the disabled region in your Amazon S3 account. This can typically be done by an AWS account administrator or someone with the necessary permissions through the AWS Management Console.
Please follow the reference link - https://docs.aws.amazon.com/accounts/latest/reference/manage-acct-regions.html
PS: View Drag, Drop & Upload Files to Amazon S3, a Salesforce AppExchange app for moving files from Salesforce to Amazon S3: https://appexchange.salesforce.com/appxListingDetail?listingId=a0N3000000B5ZPqEAN