Perform the following in the Azure Console:

1. Go to Network Watcher
2. Right click on the subscription name and click on Enable network watcher in all regions

Perform the following in Azure Command Line Interface 2.0:

Configure the Network Watcher for your subscription.

az network watcher configure –locations <locations space separated list> –enabled [true] –resource-group <resourceGroupName> –tags key[=value] key[=value]

References:

1. https://docs.microsoft.com/en-us/azure/network-watcher/network-watcher-monitoring-overview
2. https://docs.azure.cn/zh-cn/cli/network/watcher?view=azure-cli-latest#az_network_watcher_list
3. https://docs.azure.cn/zh-cn/cli/network/watcher?view=azure-cli-latest#az_network_watcher_configure