FlexClip provides 3 plans for you: free plan, plus plan, and business plan. Every plan has limits on the resources or features of editing videos.
If you paid for the Plus plan, and the elements in your project have exceeded the limits of your current plan, then it will ask you to upgrade your plan to download the project. You can also choose to download the video with a FlexClip watermark.
Please check more details at https://www.flexclip.com/pricing.html.