Federation tester says OK, yet cannot federate (403: Forbidden)

This issue has been migrated from [#16571](https://github.com/matrix-org/synapse/issues/16571).

---

### Description

After migrating postgres database from the server to the same server, synapse cannot federate.
The homeserver cannot sync any messages

Postgres logs show:
```
LOG: couldnt recieve data from client: Connection reset by peer
LOG: unexpected EOF on client connection with an open transaction
```

NGINX logs show:
```
[error]: *26081 no live upstreams while connecting to upstream, client: x.x.x.x; server: matrix.domain.net
```

### Steps to reproduce

- backup db
- delete data_directory
- create data_directory
- import db
- start hs
- cannot federate

### Homeserver

my homeserver

### Synapse Version

1.95.0

### Installation Method

Docker (matrixdotorg/synapse)

### Database

Postgres version 15.0, one single server

### Workers

Single process

### Platform

Debian 12 on a VPS VM, AMD EPYC CPU with 4GB of memory.
the package is installed through apt

### Configuration

I have implemented sliding sync

### Relevant log output

```shell
2023-10-29 10:53:00,377 - synapse.http.matrixfederationclient - 718 - INFO - sync_partial_state_room-2-$Rx-JViAFTq10Y9nO6Hv17DWglGcfL2Qk__FTWmJ7Wb4-$KeGLFuN9E72fgishOMUsU6rh9J3wAbaTmfWIDAxqcak - {GET-O-3} [libera.chat] Got response headers: 403 Forbidden
2023-10-29 10:53:00,377 - synapse.http.matrixfederationclient - 808 - WARNING - sync_partial_state_room-2-$Rx-JViAFTq10Y9nO6Hv17DWglGcfL2Qk__FTWmJ7Wb4-$KeGLFuN9E72fgishOMUsU6rh9J3wAbaTmfWIDAxqcak - {GET-O-3} [libera.chat] Request failed: GET matrix-federation://libera.chat/_matrix/federation/v1/state_ids/%21ugBhqCIFYAcsUTyxIW%3Alibera.chat?event_id=%24KeGLFuN9E72fgishOMUsU6rh9J3wAbaTmfWIDAxqcak: HttpResponseException('403: Forbidden')
2023-10-29 10:53:00,378 - synapse.handlers.federation_event - 1176 - WARNING - sync_partial_state_room-2-$Rx-JViAFTq10Y9nO6Hv17DWglGcfL2Qk__FTWmJ7Wb4 - Error attempting to resolve state at missing prev_events: 403: Forbidden
```

### Anything else that would be useful to know?

using NGINX as reverse proxy