The error message seems to be clear: you have reached the free service limit.
Please note our free service is designed for personal and casual use only. Free service users usually use our client software, such as FileManager, Online Backup and Drive Mapping, as well as our website and mobile apps. Many 3rd party programs are also supported, e.g. FileZilla and other GUI-based FTP client.
The free service does not include all advanced features; certain features are restricted, e.g. a free user can only have two concurrent connections. Also free service users shall not use any automatic software, script or device that keeps connecting to our server.
Further, we can offer very limited support to free service users if they use 3rd party software.
If you use the service for business, please order at least the lowest level subscription, which costs only $1.99/month. If you order annually, you can save 2 months for only $19.99/year.