Issue ID (e.g 10881) is different from the issue key (e.g. DEMO-523). Issue key can change for the given issue if it is moved to another project while issue id does not change.
Issue ID might change when you move data/issues from one Jira instance to the other one.
The simplest way to get Jira issue ID is to:
- open the issue page
- click the three dots "..." menu button
- mouse over the "Clone" action
- read the issue ID from the URL displayed by the browser at the bottom of the window