MO2 Login Failure (SSL Error): Outdated Windows TLS Root CA

[2mough]

The problem:

All of the sudden MO2 can't login to Nexus and closes itself immediately. I can download files manually from Nexus, but they can't be managed by MO2 because it won't stay open. Worked fine until 5/28/2026.

To Reproduce:

Steps to reproduce the behavior:

1. Launch Mod Organizer 2
2. Receive Notification
3. Cry A Lot

Environment:

• Mod Organizer Version: 2.5.2

[crazychicken0]

Same thing happening to me.

[2mough]

I checked the Nexus Discord, and they said it is not a problem on their end. Vortex users are not having the same issue, in case that is helpful for solving the problem somehow. It would seem many other MO2 users are reporting the same issues there.

[SparkGNRK]

Just got the same issue, getting SSL error after Checking API key when I try to reconnect.

[77cats]

I got the same issue since today (after 18:00 BST).

[Silarn]

If Nexus has shut down the old key validation endpoint the only solution is to use the current beta build. Vortex probably doesn't use it anymore.

[Dergash]

Same issue

[Al12rs]

Apparently it's that the bundled libssl are signed with an old cert, while the new updates started using a different ones.
Try renaming the libssl-3-x64.dll in the MO2 install folder to something and see if that fixes it (it should fall back to using the default windows lib instead that should be be signed with the new cert)

We need to release MO2 with updated bundled libssl to fix.

This doesn't seem to be a Nexus issue

[JonathanFeenstra]

Duplicate of #2402. The error also occurs in the latest dev build during the https://api.nexusmods.com/v1/users/validate.json request here:

modorganizer/src/nxmaccessmanager.cpp

Line 202 in c097670

m_Reply = m.get(request);

It detects the SSL certificate expired even though it isn't (it was renewed earlier today). If you try the same request in for example Postman, it works fine.

Update: I had a leftoverlibssl-3-x64.dll file, deleting it fixed the error.

[Dergash]

Renaming "libssl-3-x64.dll" to "libssl-3-x64.dll2" did fixed the issue

[neutralboolean]

Just adding to the data, although it seems the cause was found: I entered the API key manually, copying and pasting from Nexus's site and was still hit with

[77cats]

Renaming the dll worked. Thanks!

[Silarn]

This could potentially be a problem on the betas even if we don't ship openssl because it'll pick up any openssl on the path and use that. So we should either stop shipping the qopensslbackend.dll or ship openssl again. The former is probably the easiest option.