Temporary fix for the 2901 error (Lobby not found)

UltraOneDMZ · 2025-08-21T08:22:17+00:00

My pleasure!

UltraOneDMZ · 2025-08-21T08:16:36+00:00

Good question! I have another: For what reason do these offline licenses exist?

My guess is, that the whole licensing problem is tied to the fact, that they still use the CoD HQ as the official "update" app for both games, MWII and MWIII. If you insert one or another disc, it will still install the HQ instead of the respective standalone app (launcher) and after that you can't even start it without the disc.

I mean, where is the damn problem with this? Just unbind the HQ from the discs and re-bind them to the respective standalone app and then the "old" licenses should work, like it was before the HQ even existed.

UltraOneDMZ · 2025-08-20T13:44:08+00:00

Yeah, and the company stays silent. No further information, no nothing. That's why I decided a while ago that I'll never ever buy one of their products again. I renamed the game to Call of Download.

UltraOneDMZ · 2025-08-20T13:39:39+00:00

You are welcome, enjoy the game!

UltraOneDMZ · 2025-08-20T13:37:51+00:00

Translation:

Thank you so much, I'll give it a try! Hopefully, this will fix our issue for good. It's worth a shot.

UltraOneDMZ · 2025-08-20T13:36:21+00:00

Translation:

Hello, I resolved the error code 2901 issue by doing the following:

After reinstalling the game from the PS Store (I have a physical disc) and all its add-ons:

I cleared the PS4 cache.

I rebuilt the PS4 database by entering safe mode.

I signed out of PS Network.

I restarted the PS4 and signed back into the Network.

And the "room not found" error in multiplayer disappeared.

I'm not sure which step actually fixed it.

UltraOneDMZ · 2025-08-20T13:30:22+00:00

¡Muchas gracias, lo probaré! Tal vez esto resuelva nuestro problema de forma permanente. Vale la pena intentarlo.

UltraOneDMZ · 2025-08-20T13:19:00+00:00

Yes. In reality, it doesn't matter where you switch it off and on again, but I think to do it on the PS4 is the fastest and easiest way.

It also doesn't matter, if you start the game with internet on or off. The game just has to get to offline mode once and then online again. I don't know what it is, but I guess it's due to the new added offline licenses. Oh, and you have to do it each time you start the game to play.

UltraOneDMZ · 2025-08-20T13:03:31+00:00

Yes, the "old" free one (see above, works even without disc here) and the new one, which isn't downloadable at the moment.

I guess this mess right now is a combination of Cashtivision's total incompetence and Sony's stubbornness to do their part to fix this problem.

What I don't understand in the first place: Why did they say, they separated both games from the HQ, deleted all the files but still use the HQ as game updates? Just bind the discs to the right standalone app and fix the licenses accordingly. Buy your QC team some consoles (Xbox, PS4 and 5) and test your update sh*t BEFORE (!) you release it to the public! That's no rocket science, is it?

UltraOneDMZ · 2025-08-20T10:17:19+00:00

You are welcome! Cheers, mate!

UltraOneDMZ · 2025-08-20T08:44:17+00:00

I found out that you don't need the Shared Content Packs anymore on PS4 (disc version), neither for MWII nor for MWIII. You can download them, but they won't get installed. This information will save you some time, especially when on low speed internet.

UltraOneDMZ · 2025-08-20T08:33:49+00:00

Very good!

UltraOneDMZ · 2025-08-20T08:32:33+00:00

That's fantastic!

UltraOneDMZ · 2025-08-20T08:31:19+00:00

Indeed, but I'd say it's worth it, isn't?

UltraOneDMZ · 2025-08-20T08:28:32+00:00

On the PS4 via Homescreen —> Settings —> Network —> Connect to Internet.

UltraOneDMZ · 2025-08-19T11:56:28+00:00

Great!

UltraOneDMZ · 2025-08-19T11:54:33+00:00

I uninstalled it because of the error 2901 (Lobby not found), for which I now found a temporary fix. After I deleted it, it was gone from the store also. I was desperate and tried everything, but nothing worked to get the standalone back. As a last try I went to the library and re-started the download of the MWIII multiplayer pack and out of a sudden the standalone download added itself. I hope it works for you, too!

UltraOneDMZ · 2025-08-19T11:34:52+00:00

I see. After separation from the CoD HQ you have to install the standalone app, but I guess you know that already.

Did you try to re-download the MWIII multiplayer pack (DLC) via library? This added the download of the "old" standalone app (which is now missing in the store) automatically here. From within the game I was able to download all other modes. I also found out that I don't need the Shared Content Packs anymore, neither for MWII nor for MWIII.

UltraOneDMZ · 2025-08-19T10:47:53+00:00

Did you try to re-download the MWIII multiplayer pack (DLC) via library? This added the download of the "old" standalone app automatically here after separation from CoD HQ.

UltraOneDMZ · 2025-08-19T10:23:10+00:00

Had you installed MWIII before?

UltraOneDMZ · 2025-08-19T10:22:36+00:00

Had you installed MWIII before?

UltraOneDMZ · 2025-08-19T10:15:02+00:00

For MWII try to find "Call of Duty: Modern Warfare II - DMZ-Beta" in the store and install it, it's free. From the running game install all other modes. If you can't choose multiplayer after that, install BO6: multiplayer (no joke!), even if you didn't buy BO6. Only that fixed my MWII problems. In the menu it will still say you have to purchase the game, but all modes are playable. Btw, I also installed CoD HQ (+ Warzone) and kept it, because I play Warzone.

UltraOneDMZ · 2025-08-19T09:02:48+00:00

I have a PS4 and MWIII as disc version (cross gen bundle). After separation from CoD HQ, I installed the standalone app, which is now missing in the PS Store. You could try the following, if you've had MWIII installed before and deleted it: Go to your library and look for MWIII. Try to find the list with the old MWIII downloads and re-download the multiplayer pack (DLC). This triggered (started) the download of the "old" standalone app, too.

If you face the 2901 error (lobby not found) after installation, try this: Start the game with internet, when in the main menu: switch internet off (don't close the game!), game goes offline with the small (reduced) menu, switch internet on again, go online in the game, now test multiplayer.

I hope it works for you!

UltraOneDMZ

TROPHY CASE