Cannot modify Postgres RDS instance class in us-east-1e

I am getting the below error when trying to change a Postgres RDS db.t2.small instance class in the us-east-1e availability zone to ANY/EVERY other instance class. I need to do this before PG 9.6 retires on 1/18/22 as current instance class is not supported for required upgrade.

I have read in post below that this could be a misconfiguration on AWS end. If not, when will capacity be added to us-east-1e? https://repost.aws/questions/QUYNaeNfHOTOKZCSopE5IdnA/rds-r-6-g-no-instances-of-the-requested-class-available

We're sorry, your request to modify DB instance <INSTANCE NAME> has failed. Cannot modify the instance class because there are no instances of the requested class available in the current instance's availability zone. Please try your request again at a later time.