RDS with Cloud Formation and AZ issues

Question

I am using cloud formation to create a setup containing an RDS instance.

I am having some difficulties creating the RDS Instance on the account of the following error:

Answer 1

Just to add more details about this problem. I solved my problem evaluating subnet group at RDS > subnet group. (Subnet group is a concept that exists only in RDS context. Not in VPC context)

In my case there was a subnet group created automatically first time I tried to create a RDS Mysql selecting my personalized VPC (not default VPC) but I think RDS script created a subnet group selecting the first 3 subnets from my VPC:

• subnet1 region 1a,
• subnet2 region 1a,
• subnet3 region 1b

I created 3 private subnets to use with RDS:

• subnet4 region 1a,
• subnet5 region 1b,

• subnet6 region 1c

  Its not possible to modify a subnet group then I created one and then select 3 subnets with the same acl and route configuration, each one in a different region (1a,1b,1c). Then I deleted that another misconfigured subnet group. Back to RDS dashboard click in Create RDS, choose all database details you want, select the desired VPS and you see the selected subnet group name . Problem Solved.