Some Jira instances use the IP Allowlist to limit access to Jira.
This may block the app and the following error message is displayed:
The app is hosted on Atlassian Forge platform which uses following IPs:
52.195.248.93/32 54.65.219.119/32 43.207.238.123/32 3.114.146.111/32 54.248.180.178/32 57.180.171.119/32 13.209.252.121/32 15.165.21.19/32 43.202.223.238/32 3.34.8.241/32 3.37.121.177/32 3.34.165.169/32 15.164.153.22/32 43.201.237.75/32 13.200.51.21/32 13.200.127.18/32 65.2.173.31/32 15.206.230.70/32 3.7.242.212/32 43.205.183.186/32 54.255.41.156/32 52.77.196.9/32 18.143.11.169/32 18.142.175.136/32 54.254.13.217/32 52.220.108.50/32 3.104.191.162/32 13.238.244.22/32 3.106.172.84/32 52.65.164.184/32 13.237.143.132/32 3.105.255.118/32 3.98.151.27/32 3.96.73.34/32 35.182.178.44/32 15.156.32.59/32 15.222.164.249/32 15.156.255.184/32 18.153.162.220/32 18.157.151.173/32 3.126.237.94/32 18.196.69.189/32 52.58.86.18/32 3.77.185.155/32 16.63.156.232/32 16.63.10.60/32 16.63.133.73/32 16.63.192.113/32 16.63.86.27/32 16.63.153.19/32 54.220.63.40/32 54.154.186.82/32 52.208.56.204/32 54.76.137.153/32 34.253.103.242/32 63.34.104.55/32 13.43.10.138/32 18.132.72.151/32 13.43.238.10/32 13.43.230.20/32 13.42.94.26/32 13.41.178.119/32 18.229.170.213/32 54.232.43.18/32 52.67.212.82/32 54.94.144.45/32 15.229.167.123/32 177.71.171.149/32 3.224.137.93/32 52.55.61.132/32 54.156.218.101/32 34.194.247.143/32 3.220.210.28/32 34.231.161.126/32 34.194.73.28/32 3.231.15.71/32 54.241.128.19/32 13.56.84.222/32 52.53.140.163/32 54.193.160.145/32 54.218.196.28/32 35.160.6.102/32 18.236.52.165/32 52.43.192.52/32 34.215.254.205/32 54.214.155.219/32 54.190.195.254/32 52.89.100.78/32
If you add these IPs to the allowlist, the app will function as expected.
See also https://support.atlassian.com/organization-administration/docs/ip-addresses-and-domains-for-atlassian-cloud-products/