Issue Summary

When creating an RoadMaps plan, users encounter a misleading error message: "Your plan contains more than 100 projects. Remove issue sources or use the section below to refine your plan." This occurs specifically when REST request ( /rest/jpo/1.0/plan/setup/project) is blocked, not because there are actually more than 100 projects in the plan.
This is reproducible on Data Center: yes

Steps to Reproduce

1. Ensure that access to /rest/jpo/1.0/plan/setup/projects is blocked (on the firewall) causing any requests to this endpoint to be rejected return an empty result.
2. Attempt to create an RoadMaps plan

Expected Results

• The Jira plan creation page should handle all network or permission errors gracefully and provide a clear and accurate error message to the user.
• The error message should inform the user that the REST request could not be completed due to a network or permissions issue.
• The error should not be misleading or suggest incorrect causes, such as implying an issue with the number of projects when the actual problem is network-related.

Actual Results

• When the REST request for /rest/jpo/1.0/plan/setup/projects is blocked, the Jira plan creation page incorrectly informs users that "Your plan contains more than 100 projects. Remove issue sources or use the section below to refine your plan."

Workaround

• Currently, there is no alternative method or workaround that can be applied within JIRA to bypass the issue. To resolve this issue, the blockage on the firewall for the REST endpoint /rest/jpo/1.0/plan/setup/projects must be removed.