What stands out to me the most here is that your service switched over to the new VM. What is pointing your users to the new VM? Are you using reverse proxies, gateways, load balancers, containers...etc?
This is a good start to get an idea for creating a test environment:
https://confluence.atlassian.com/adminjiraserver/creating-a-test-environment-for-jira-966063324.html
When I made test environments for our Atlassian stack, I made sure that they were on separate networks than the production servers. So, for Azure I would place these VMs in a seperate VNET.