Clients cannot connect to Synapse after restored backup

[matalb]

What type of hardware are you using: VPS bought online
What YunoHost version are you running: 12.1.171
What app is this about: Synapse

Describe your issue

After an unsuccessful upgrade of Synapse, I restored the last backup which ran without errors.

Now, I cannot connect to the Synapse homeserver with any client. Error messages are below.

Only once during the recent days, another user on matrix.org could read a test message sent from my android device, although my Element client signalled an error.

Installed Synapse version: 1.136.0~ynh1

Share relevant logs or error messages

element-desktop (Linux):

Sent messages will be stored until your connection has returned.

element/android: error on the top-level bar: Connectivity to the server has been lost or in some cases at the bottom of the last unsent message: Messages failed to send with the options retry or delete.

[matalb]

What I have tried so far:

• Logged out from element-desktop
• Tried to login again. These are the issues:
  • MYDOMAIN.TLD isn’t recognized as a matrix server as it was before.
  • SUBDOMAIN.MYDOMAIN.TLD is accepted
  • Login via CAS results in endless spinning
  • After terminating element-desktop and restarting, Element GUI is shown, but with empty persons and room list

I wonder whether Synapse is just misconfigured, but have no idea where to look.
Any help is very welcome.

[matalb]

Looking for options to debug Synapse server:

• Is it a permission problem?
• are the domains a problem?
• which client gives more debug information?

[matalb]

I would really appreciate any help whatsoever. Synapse is not working after having restored it from backup.

It would be better than nothing, if I could do this:

• uninstall Synapse completely
• install Synapse again

My question is: Is every Yunohost user automatically a Synapse user as before?

Are just the old chat messages lost?

Thank you for every help!

[matalb]

Now I did a complete new installation of Synapse resulting into issues again. I suspect my server configuration. The domain is SUBDOMAIN.MYDOMAIN.TLD, the server name MYDOMAIN.TLD.

I read the post-installation notes. The suggest to define a SRV record in the DNS configuration:

_matrix._tcp.SUBDOMAIN.MYDOMAIN.TLD. 3600    IN      SRV     10 0 8448 SUBDOMAIN.MYDOMAIN.TLD.

1. The dots after TLD. look strange. Are they realy meant like that?
2. I am not sure how to “open the TCP port 8448 on your ISP box”. But Synapse has been working for 3 or 4 years without major problems.
3. Logging in with Element-Desktop, it complaints about MYDOMAIN.TLD being not a valid matrix homeserver although I stated MYDOMAIN.TLD as domain name in the Synapse settings. With homeserver SUBDOMAIN.MYDOMAIN.TLD I can login using my matrix id. All chats and rooms are lost because Synapse was blank.

Again, any help or tipps or hints will be appreciated.

[matalb]

With the new installation, I have to join every room again. The whole history is lost.

What migh be the reason that the backup cannot be restored?