Check your firewall rules with the following command: gcloud compute firewall-rules list with this, you can review the VPC where the VM instance was migrated; and if it has allowed the Ingress TCP: 22 Port, you will see something like this:
NAME: testmivpc-allow-ssh
NETWORK: testmivpc
DIRECTION: INGRESS
PRIORITY: 65534
ALLOW: tcp:22
DENY:
DISABLED: False
If this firewall rule is missing, you can add the firewall rule in the GCP console -> VPC Networks ->select your VPC network _Click on the firewall rules to double check that the tcp: 22 port is allowed.
If the issue still is ongoing after checking the firewall rules, you can follow this guide to start troubleshooting SSH connection .