Hello movieguy-13,
We see from your post that you were unable to send an attachment with Mail Drop, and we'll be glad to assist you.
These are some reasons why you might see this alert:
• Your internet connection cannot reach the Apple servers.
If you've continued to encounter this alert, try to connect to another network.
If that's not an option, then check if your proxy or VPN settings are blocking the required ports. Open this link to view the TCP and UDP ports used by Apple software products,
• You've reached the Mail Drop limits.
Let us know if you need additional help and we'll guide you forward.
All the best!