Can't open my mod manager.

Whenever i try to open the mod manager i get a little tone and a notification the says "Could not load fxml view for theme/modmanager.fxml". When i went to that folder it was empty. I have no idea wheat to do.

Are we talking about the game, or the client?

A work of art is never finished, merely abandoned

The client I guess. Try reinstalling it.
After you have uninstalled it, check manually if the installation folder is really empty and delete it if not. Then install the client again.

Client and it turns out if I enter a lobby then exit it works. I did try An uninstall/reinstall cycle with no change

Same problem. Reinstall doesn't help

As far as I can see, nothing is being created in the themes folder. To fix this, the client reinstalled with the complete removal of configs and even changed the security policy for the folder C:\ProgramData\FAForever\themes full access for everyone. None of this helped.
The problem itself has arisen quite recently, about a week at most.

It is because the client is using the theme file it comes packaged with. The issue is that the client has trouble parsing the active mods of the game.prefs file. But I have not been able to reproduce the issue even with the mods stated so likely it is something special to a specific version of the mod or your file system

I have removed all mods and when trying to create a game I get this:

java.util.concurrent.CompletionException: NotifiableException(i18nKey=mod.errorUpdatingMods, i18nArgs=[])
at org.springframework.aop.interceptor.AsyncExecutionAspectSupport.lambda$doSubmit$3(
at java.base/java.util.concurrent.CompletableFuture$
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(
at java.base/java.util.concurrent.ThreadPoolExecutor$
at java.base/
Caused by: NotifiableException(i18nKey=mod.errorUpdatingMods, i18nArgs=[])
at com.faforever.client.mod.ModService.writeModStates(
at com.faforever.client.mod.ModService.overrideActivatedMods(
at com.faforever.client.mod.ModService.updateAndActivateModVersions(
at com.faforever.client.mod.ModService$$FastClassBySpringCGLIB$$aae9cfd3.invoke(<generated>)
at org.springframework.cglib.proxy.MethodProxy.invoke(
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(
at org.springframework.aop.interceptor.AsyncExecutionInterceptor.lambda$invoke$0(
at org.springframework.aop.interceptor.AsyncExecutionAspectSupport.lambda$doSubmit$3(
... 4 more
Caused by: java.nio.charset.MalformedInputException: Input length = 1
at java.base/java.lang.String.throwMalformed(
at java.base/java.lang.String.throwMalformed(
at java.base/java.lang.String.newStringNoRepl1(
at java.base/java.lang.String.newStringNoRepl(
at java.base/java.lang.System$2.newStringNoRepl(
at java.base/java.nio.file.Files.readString(
at com.faforever.client.mod.ModService.writeModStates(
... 13 more

We found the cause of this issue, but no definitive solution yet.

A work of art is never finished, merely abandoned