I am trying a small example with AWS API Gateway and IAM authorization. The AWS API Gateway generated the below Endpoint :
https://xyz1234.execute-api.us-e
Faced similar issue when I use timedatectl command to change datetime of underlying machine... Explanation given by MikeD & others are really informative to fix the issue....
sudo apt install ntp
sudo apt install ntpdate
sudo ntpdate ntp.ubuntu.com
After synchronizing time with correct current datetime, this issue will be resolved