OSProvisioningTimedOut while creating VM from a custom Linux VHD

Hi All,
I have followed the steps to make a custom VHD for a Linux VM using the following resources:
https://learn.microsoft.com/en-us/azure/virtual-machines/extensions/update-linux-agent#oracle-linux-6-and-oracle-linux-7
https://learn.microsoft.com/en-gb/azure/virtual-machines/linux/oracle-create-upload-vhd?WT.mc_id=Portal-Microsoft_Azure_Support#oracle-linux-64-and-later
https://learn.microsoft.com/en-gb/azure/virtual-machines/linux/create-upload-generic#general-linux-installation-notes

My custom Linux VHD is of fixed size and created using Hyper-V
I am still getting the following error:
{
"code": "DeploymentFailed",
"message": "At least one resource deployment operation failed. Please list deployment operations for details. Please see https://aka.ms/DeployOperations for usage details.",
"details": [
{
"code": "OSProvisioningTimedOut",
"message": "OS Provisioning for VM 'testVMappsvr' did not finish in the allotted time. The VM may still finish provisioning successfully. Please check provisioning state later. Also, make sure the image has been properly prepared (generalized).\r\n * Instructions for Windows: https://azure.microsoft.com/documentation/articles/virtual-machines-windows-upload-image/ \r\n * Instructions for Linux: https://azure.microsoft.com/documentation/articles/virtual-machines-linux-capture-image/ \r\n * If you are deploying more than 20 Virtual Machines concurrently, consider moving your custom image to shared image gallery. Please refer to https://aka.ms/movetosig for the same."
}
]
}

Is there anything else which i can try out? How do I debug this and find out what is wrong?
Is there a tool which will help me in checking my VHD before uploading, that will tell me all is ok for creating an image/VM on azure from VHD?

Thanks,
S