Please include information on whether you built Gitea yourself, used one of our downloads, are using https://try.gitea.io or are using some other package
Please also tell us how you are running Gitea, e.g. if it is being run from docker, a command-line, systemd etc.
If you are using a proxy or a CDN (e.g. Cloudflare) in front of Gitea, please disable the proxy/CDN fully and access Gitea directly to confirm the issue still persists without those services.