If you or your organization use restrictive firewall or proxy server settings, you or your network administrator may need to allow-list certain domains and IP address ranges to ensure Atlassian cloud.
Jira Premium customers can limit access to Jira based on the IPs. It's a common settings to increase the security of company data. Along with that settings, there is a list of IP addresses that are allowed to talk with Jira instance. It's called IP allowlists.
On that list you have to add all IP ranges used for ingress and egress to get the Jira working. Atlassian provides an 8 IP addresses that are responsible for handle Forge apps requests. To get the Forge app working on your instance, you have to add them to you allowlists.