It sounds like a normal thing. Links created for any file without a PRO account will be available for only 2 days, after that the link and any files connected to it will be removed.
Share your files via Link:
1. Drag and drop your files to any part of the website or click the "Click here" button to choose the files you want to share,
2. Click the "Create download link" tab,
3. Enter your email address,
4. Click the "Password protection" checkbox if you want add a password,
5. Click the Create button to upload your files and create the download link you can share with your contacts.