According to the log file NetDrive was trying to access tt-a-c bucket using following URL:
and the server returned ‘access denied’.
<?xml version="1.0" ?>
<Error>
<Code>AccessDenied</Code>
<Message>Access Denied.</Message>
<BucketName>tt-a-c</BucketName>
<Resource>/</Resource>
<RequestId>165F2EB90AE6564B</RequestId>
<HostId>51418aec-6121-444c-a34a-338392109072</HostId>
</Error>
I think you need to check server log.