Amazon S3 sync not working

KeePass Version: 2.18
KeePassSync Version: 6.0.10.1

I have set up KeePassSync to sync to Amazon S3. I have a bucket created and confirmed the access credentials are correct. Once configured, if I go to Tools > KeePassSync > Open..., "digitalbucket.net" is the selected Online Provider. Changing this to S3, reconfirming my account details, and selecting OK displays the following error:

KeePassSync

Possible connection issue. Unable to retrieve databases. Test your connection and try again.

OK

When I go back to the previous dialogbox, digitalbucket.net is once again selected (although Tools > KeePassSync > Options does show S3 as the selected provider). If I select Tools > KeePassSync > Sync, I receive the following error:

KeePassSync

KeyPassSync_S3: Please re-send this request to the specified temporary endpoint. Continue to use the original request endpoint for future requests.

at System.Web.Services.Protocols.SoapHttpClientProtocol.ReadResponse(SoapClientMessage message, WebResponse response, Stream responseStream, Boolean asyncCall)

at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters)

at KeePassSync.AmazonS3.AmazonS3.GetObject(String Bucket, String Key, Boolean GetMetadata, Boolean GetData, Boolean InlineData, String AWSAccessKeyId, DateTime Timestamp, Boolean TimestampSpecified, String Signature, String Credential)

at KeePassSync.Providers.S3.S3Provider.GetFile(PwEntry entry, String remoteFilename, String localFilename)

OK

Currently, I must manually sync to S3 by going to the S3 console and uploading the files. Any ideas on what may be causing this?

Thanks for your help.