I am sorry you are having trouble with the Modern view of Garmin Connect. I am confused about this thread because Garmin Express doesn't know what version of Connect you use. Garmin Express just uploads the data to a database which was used by both versions. Please answer the following so we have a better understanding of what you mean:
What version of Garmin Express are you using? (This is found in the settings under "About".)
At what point in the upload process are you stuck?
Are you getting an error message?
What version of Windows are you using?
What is the serial number of the Dakota 10?
Feel free to include more information if you think it will explain the situation better. When we understand the problem better, we should be able to assist you better.
Garmin Express 4.1.17.0 I connect my Dakota 10, Garmin Express sees it, Garmin Connect doesn't - I didn't need to have Express running with Classic view No error message, all I get is 'Nothing To Sync' Windows 7 at home, Windows 8.1 at work where exactly the same thing happens S/N: 1pk006400
I am sorry that you are having trouble syncing your data. Garmin Express will not sync GPX files so they will need to be uploaded manually in Garmin Connect. For instructions, please see the FAQ How do I manually upload data from USB Mass Storage devices to Garmin Connect?