Can't join MP, steam joining Xbox host

[slow bear]

Title: My partner is hosting a co-op game on Xbox series X, working normally, I can't join from my PC (Steam).

Reproduction Steps: Xbox series X is hosting, I click on co-op in the menu, navigate to the 'join' tab, enter in the session code from the host, the screen says 'connecting to server' for about 1 min, then error code 'Your connection is unstable. Please Try again later'' comes up.

Repro Rate: Every time, tried since 1.2 came out, every patch the same

In-Game Date & Time: Any time of the playable day.

Players & Platform: Host: Xbox series X, Joining from PC/Steam

Game Version: Xbox: 1.2-1242, PC:1.2-1242

Input Mode: Xbox: controller, PC: Keyboard and mouse

PC Specs:
OS:MS Windows 11 Home
MB: X870 AORUS ELITE WIFI 7
CPU: AMD Ryzen 7 9800X3D (8 cores) ,water cooled
RAM: 64GB of DDR5 (6000MT/s)
GPU: NVIDIA GeForce RTX 5090
Storage: SSDs
Connection: Ethernet, connected to a simple switch, Xbox is connected to the same switch, so both devices are on the same LAN.

Attachments (if available):
Image of the issue

[devout hill]

Hi there @slow bear , thank you for reaching out to us! Have you tried changing your connection to see if it resolves the issue?

[slow bear]

Hi, we have tried connecting via wifi on both devices and via hotspot on mobile networks as well, no change unfortinately.

[devout hill]

From the current findings, it appears that the issue may be related to the player’s connection. As a temporary workaround, we recommend trying to switch your internet connection to see if that allows you to play co-op successfully.

That said, if you're confident that you have a stable connection, we’d like to narrow things down further. Could you please run a quick internet speed test at https://www.speedtest.net/ and share the results with us? It would also be very helpful if you could let us know whether you’re using Wi-Fi or a LAN cable.

Thanks in advance

[slow bear]

Hi Shei, we will do a check and connect to a different internet connection, we have tried wifi and mobile previously, and a mix of both. Thank you for your help, please let us know if there is anything else we should try! We are using a LAN cable connection currently, going to a simple switch which is also connected to the WAN via our router.

[slow bear]

@devout hill It is worth noting that we are both on the same LAN network connected to the internet, the Xbox host has no issues connecting to the multiplayer server.

[devout hill]

Thank you for sharing this information with us! I'll relay this to the team for checking and I'll reach back to you if we need more information

[lost socket]

I played from steam with my wife who played on PS5. Last night (31/10/25) we played as usual, but studently at 00.00am (1/11/25) I disconnected from the host (ps5) and cannot join untill now. I tried make a new co-op game as a host; my wife also can't join to my room with same error message. We play with same internet access.

[devout hill]

Hi there, I'm sorry to hear that you're also experiencing similar issue. Have you tried verifying your file integrity to see if it resolves the issue? To do so, please follow the steps below:

• Open Steam → Go to Library
• Right-click Coral Island → Select Properties
• Go to Installed Files → Click Verify Integrity of Game Files
• Restart Steam and try launching the game

[astral arrow]

@chilly patio I can't find the post that you made on there anymore, but try the internet speed test and ethernet cord to verify this isn't a network issue (which it REALLY doesn't feel like with all the testing we ran yesterday). Esepecially since there was no changes in your internet over the course of <24 hours. We had been playing fine the night before and now it hasn't worked for weeks? The game isn't even found anymore.

And we verified that the game is being hosted by another friend able to join our game all 3 of us were playing.

We did a LOT of testing.
Removed the Coral Island folders from steamapps and appdata
Turned off cloud sync on all of steam games as well as Coral Island.
Uninstalled.
Restarted PC.
Reinstalled.
@chilly patio was still unable to host a game or see any games I hosted (new or otherwise) via direct inventation or invite code.

This has been going on for 3+ weeks and I am so so frustrated now

[devout hill]

We’re really sorry for the trouble this issue has caused — we completely understand how frustrating it is not being able to play with your friends. 🙏

Thank you so much for always sharing details and going through the troubleshooting steps with us. We’ve relayed all the reports and details to the team so they can take a closer look at this matter.

We’ll share an update here: https://discord.com/channels/623097219628662784/1406061246020583635 once we have more info. Please feel free to follow the thread for any update and let us know if you notice any changes on your end too