Problem Definition

Currently, when moving Jira and Confluence Server/DC to Jira/Confluence Cloud, the new Cloud site has new URLs, which affects Confluence pages linked in the Jira "Environment" system field.
 

Suggested Resolution

Confluence links in the Jira "Environment" system field need to be updated to match the cloud URLs

Temporary Resolution

In this case you contact Atlassian support by logging a request in support.atlassian.com and ask them to apply the workaround for this issue.
 
The team will try to follow a workaround under the boundaries of https://confluence.atlassian.com/confkb/after-a-successful-server-to-cloud-migration-url-links-are-broken-in-the-new-cloud-instance-1077781093.html to fix the problem.