[2025.06.11-16.00.22:098][820]LogFab: Display: Logging in using persist
[2025.06.11-16.00.22:098][820]LogEOSSDK: Warning: LogEOSAuth: No existing persistent auth credentials were found for automatic login.
[2025.06.11-16.00.22:114][820]LogFab: Error: Login failed - error code: EOS_InvalidAuth
[2025.06.11-16.00.22:114][820]LogFab: Display: Logging in using exchange code
[2025.06.11-16.00.22:114][820]LogFab: Display: Reading exchange code from commandline
[2025.06.11-16.00.22:114][820]LogEOSSDK: Error: LogEOSAuth: Invalid parameter EOS_Auth_Credentials.Token reason: must not be null or empty
[2025.06.11-16.00.22:136][821]LogFab: Error: Login failed - error code: EOS_InvalidParameters
[2025.06.11-16.00.22:098][820]LogFab: Display: Logging in using persist
[2025.06.11-16.00.22:098][820]LogEOSSDK: Warning: LogEOSAuth: No existing persistent auth credentials were found for automatic login.
[2025.06.11-16.00.22:114][820]LogFab: Error: Login failed - error code: EOS_InvalidAuth
[2025.06.11-16.00.22:114][820]LogFab: Display: Logging in using exchange code
[2025.06.11-16.00.22:114][820]LogFab: Display: Reading exchange code from commandline
[2025.06.11-16.00.22:114][820]LogEOSSDK: Error: LogEOSAuth: Invalid parameter EOS_Auth_Credentials.Token reason: must not be null or empty
[2025.06.11-16.00.22:136][821]LogFab: Error: Login failed - error code: EOS_InvalidParameters
This was a tough one–quite the rabbit hole. I wish I understood the cause better, but I did find a workaround, eventually.
The error was occurring in both Fab and Bridge for me. It presented on my system in the same way. I tried both binary and compiled builds, as well as a main branch build. When the editor was run from my IDE, I got the additional error: ERROR:libc_interceptor.cc(109)] Cannot find getaddrinfo with dlsym. After some digging, I found that this file is housed in the CEF file libcef.so.
The workaround is incredibly simple: change line 16 of Engine/Source/ThirdParty/CEF3/CEF3.build.cs to bool bUseExperimentalVersion = false;
This will revert the used CEF version to the other installed CEF with UE, flag/commit number 4577, which works in my case. I believe this requires a compile of the engine, so this will only work in the case that you’re building from source.
It’s odd that using an older CEF worked. I suspected I would need a newer one, as my system stays rather up to date–perhaps an odd forward incompatibility issue related to glibc or something. Here is some system info perhaps relevant to this at the time of finding the workaround:
I think a recompile/update of the used CEF may be needed for a full fix–I found that within UE, there is a whole CEF compiling script/environment: Engine/Source/ThirdParty/CEF3/Build. Over the past week, I explored compiling CEF and had poor results, however. I’ll spare you the gory details.
I’ve got UE 5.6 from the downloaded binary and (in a different directory tree) a full source build from GitHub.
I’ve built plugins locally for the prebuilt UE installation, but is there a way to use my source build to update just that one .so file in the binary engine installation?
Incidentally, when I was researching this problem during the UE 5.6 preview period, I found that there are multiple discussions online about that CEF3 interaction with libc. It was such a mess that I eventually just filed a bug report to Epic and disabled the plugin here. For that reason, I really appreciate that you found a workaround.
I notice that in UE 5.6.1 there is a mention of fixing CEF-related crashes, per UE-295044. I can’t find that issue on the bug tracker, so I don’t yet know details. I will test after I get 5.6.1 installed here.