Thank you for getting back and sharing additional details here.
I understand you tried the IP Flow verify test and you received access denied error message.
A network security group contains security rules that allow or deny inbound network traffic to, or outbound network traffic from, several types of Azure resources. For each rule, you can specify source and destination, port, and protocol.
IP flow verify returns Access denied and the name of the security rule that denies or allows the traffic, and the network security group with a link to it so you can edit it if you need to.
If you received access denied error with a link to the NSG blocking this connectivity (as per the image shown above), you can check if any particular Inbound or Outbound rule is blocking the connectivity in this NSG.
If IP Flow Verify did not provide a link to any NSG then a default security rule is denying the traffic. For more information, see Default security rules.
As the NSG implements DenyAllInbound and DenyAllOutBound rules then you need to add both inbound and outbound rules to allow communication for port 1521 from your local machine's Public IP.
On your network in Azure please check the if any NSG is associated with VM's NIC and VM's subnet and add a rule as shown below.
For Inbound Rules:
Source IP : This should be your Local Machine's Public IP
Destination IP: Your Virtual Machine's Public IP
Destination Port: 1521
For Outbound rules:
Source IP : Your Virtual Machine's Public IP
Destination IP: This should be your Local Machine's Public IP
Source Port: 1521
You can use the image below as reference
Hope this helps! Please let me know if you have any additional questions. Thank you!
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