Occasionally, the AWS defaults are set too low; for example, the default for a new account is set to 5 maximum static VPC EIPs, and those can be used up quite quickly. In order to request more, you will need to open an AWS support case. We usually recommend allocating in batches of 5 and most customers will usually request a limit to increase the VPC EIP quota to either 10, 15, or 20 for example.