Vault UI is stuck at ui/vault/init. Initialize button not working.

I started a Vault instance on an Ubuntu server. CLI works perfectly, but UI is stuck at the ui/vault/init page and I cannot login.
enter image description here

Vault is initialized and unsealed.

Config:

storage "file" {
  path    = "./data"
}

listener "tcp" {
  address     = "127.0.0.1:8200"
  tls_disable = "true"
  proxy_protocol_behavior = "use_always"
}

api_addr = "http://127.0.0.1:8200"
cluster_addr = "http://127.0.0.1:8201"
ui = true

Am I missing something? It is my first time with Vault in production mode.