Unable to ssh into VM -- connection timed out

Question

I am trying to create a VM with the Azure CLI and ssh into it from Azure Cloud Shell. I have followed the official guide (https://learn.microsoft.com/en-us/azure/virtual-machines/linux/quick-create-cli) by running these commands:

$ az group create --name myGroupName --location westus2  
$ az vm create --resource-group myGroupName --name myVmName --image UbuntuLTS --admin-username azureuser --generate-ssh-keys  

However, when try to connect via ssh with the public IP address reported by the second command above, the connection times out:

$ ssh -vvv azureuser@publicIpAddress  
OpenSSH_7.2p2 Ubuntu-4ubuntu2.10, OpenSSL 1.0.2g  1 Mar 2016  
debug1: Reading configuration data /etc/ssh/ssh_config  
debug1: /etc/ssh/ssh_config line 19: Applying options for *  
debug2: resolving "publicIpAddress" port 22  
debug2: ssh_connect_direct: needpriv 0  
debug1: Connecting to publicIpAddress [publicIpAddress] port 22.  
debug1: connect to address publicIpAddress port 22: Connection timed out  
ssh: connect to host publicIpAddress  port 22: Connection timed out  

Any suggestions on what I am doing wrong?

In addition, I have tried running these commands in Powershell on my local machine. I have found that after I create a new resource group, and then launch a VM, I am able to ssh into the VM using Powershell. But when I disconnect from the VM and then try to ssh back into it, I am unable to re-connect since it results in the timeout error. If I try to create a new VM under the same resource group, I am unable to ssh into it at all. If instead, I create a new resource group and a new VM, I can ssh into it the first time, but not on subsequent tries.

I need some help debugging this issue, since I need to be able to launch VMs, and periodically ssh into them and run some code.