Why when I'm trying to use Switchover option in "Blue/Green Deployment" I'm getting "Role" error?

Hello,

• We have a DB of 5 terabyte.
• We're using RDS Aurora 5.6.
• We built green DB of Aurora 8
• The replication is working without any issue

Today I tried to make a switchover from the "blue" to the "green" and I got this error: DB instance XXXX has a different role than YYYY

I didn't found what it mean and how to solve it.