Cloned Issues Do Not include Forms
Cloning does not copy the issue entity properties (where ProForma form data lives). Because of this, cloned issues will not inherit forms from the original issue.
There are a number of workarounds for this limitation.
Use Deep Clone (Cloud only) and select the Clone issue properties (usually used by other apps) option. This is the most convenient method in terms of usage, however might require licensing and installing another app. Read more here.
Rather than cloning the issue, change the issue type or request type. This allows for bulk changes of issues. The limitation of this method is that it is not valid if the issue needs to be cloned to a new project.
Save ProForma form data to Jira fields as described here). Clone the Jira issue, and manually add the same form as the previous issue. Because all the Jira field data will clone as expected, ProForma fields which are linked to those Jira fields will automatically populate.
Clone the issue, and then hand-copy form data from one issue to another.
Limitations Using Gaia for Jira: Project Template Manager
The Jira plugin, Gaia for Jira: Project Template Manager: (Server and Data Center) does not copy ProForma form templates with the project configuration. However, you can easily copy form templates from one project to another as described here.