There are two droplet limits, one is the number of droplets that you can spin up which you can see in your settings page:
https://cloud.digitalocean.com/settings
The second is if a customer signs up using Paypal we restrict some of the larger sizes, this is done to minimize the amount of fraud we have to deal with.
Unfortunately we deal with a high amount of abusive and fraudulent signups so we've had to instate a lot of automated filters and other updates to the user experience. It really sucks, but without it we'd have a lot more fraud which would really just make the entire experience worse overall.
In either case opening up a ticket will get either issue resolved.
Sorry for the inconvenience but if anyone is good at fraud detection and wants to help us to continue to automate it and make it smarter, we are hiring =]
Thanks,
Moisey