Yeah a lot of people have troubles logging into XBOX EU at the moment.

Same goes for PS-EU since the update, but way worse today.

I've had a response to the ticket:

Greetings!

Thank you for contacting The Elder Scrolls Online Team. My name is Chase.

I am escalating your ticket to a specialized team to ensure you receive the best possible resolution of your issue. Thank you for your patience while they review your request, they should be reaching out to you shortly.

If you have any further questions or information regarding this issue, please respond directly to this ticket to ensure the proper team is able to see your response.

Regards,

The Elder Scrolls Online Team

Had a further response:

Greetings!

Thank you for contacting The Elder Scrolls Online Team. Kyra here with the advanced team and I would be delighted to assist you today.

We're sorry to hear you haven't been able to connect back to The Elder Scrolls Online after your game crashed. Rest assured we are still looking into this for you.

The error 307 indicates that you have been disconnected from the megaserver.
Check the Service Alerts page to see if ESO is experiencing an outage or going through maintenance.
If ESO is experiencing and outage or undergoing maintenance, you will have to wait until the servers are restored to log in.
If you attempt to log back in right away, you will receive an Error 304. We recommend waiting for a period of 15-20 minutes before attempting to log in again.
The reason to wait the 15-20 minutes is that the server needs that time to "catch up" to your data. If you log back in before the server has updated your account appropriately, the server will think you are still online and your character will be booted again.
If your issue persists, we recommend trying the following troubleshooting steps:

Perform a Connection Test on the Console

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You can perform a connection test on your Xbox by following the process below:

Press the [Menu] button on the controller.
Select Settings.
Select Network.
In the second column titled Current Network Stats, check the NAT status and confirm whether it is reading that your console is running on wireless or Ethernet correctly. The NAT should show as Open.
For troubleshooting a disconnect in your connection, select Troubleshooting and then Test Network Connection.
The NAT types can be one of the following:
OPEN: Can play games with any other NAT type.
MODERATE: Can play games with open or moderate NAT types.
STRICT: Can only play against open NAT types.


Forward Ports

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The ports for ESO are as follows:

UDP Port 88
UDP Ports 12000 through 32000
UDP Port 6250
UDP Port 5060
UDP Port 5062
UDP Port 3478 through 3479
UDP and TCP Port 3074
UDP and TCP Port 53
TCP Port 80
TCP Port 433
For instructions on how to forward ports, please contact either your ISP (Internet Service Provider) or manufacturer of your modem/router.

Clear the Mac Address

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You can clear the Mac Address on your console by following the steps below:

Press Start at the main Xbox menu.
Navigate to Settings.
Select NetworkSettings, AdvancedSettings, AlternativeMacAddress, and finally Clear.
Restart and shut down the Xbox. Disconnect the power cord from the back of the console and wait two minutes.
Once the two minutes have passed, plug the power back in and wait for the power bricks light to go from white to orange.
When the light switches to orange, reboot the console and try the game again.

If the above solutions do not resolve the issue, we recommend you contact Xbox Support.
Should you have any other queries, please feel free to reach out to us and we would be happy to help.

Thank you,
Kyra
The Elder Scrolls Online Team