After installed NGINX Proxy Manager I found this error in the Supervisor log:
21-08-12 19:07:47 ERROR (SyncWorker_0) [supervisor.docker] Can’t start addon_a0d7b954_nginxproxymanager: 500 Server Error for http+docker://localhost/v1.41/containers/24c1aac720fe240d8049e4b9667326332100e2186e48e2cf59026f68f376dfaf/start: Internal Server Error (“driver failed programming external connectivity on endpoint addon_a0d7b954_nginxproxymanager (d5da242aecb80bbe5f736834ce6a82735a273a4a7b733f8a7319038c0420fd60): Bind for 0.0.0.0:443 failed: port is already allocated”)