Native Ad error but no error code

[Yoruss]

Native ads were working fine, and I noticed recently that they did not show up anymore.
After launching it with a debugger, I got an error like this one:

flutter: Native Ad: NativeAdResult.ERROR --> {invalidated: false, placement_id: 334481150913884_334484467580219, error: }

But I have no error code, and changed nothing since the code was working previously. Any idea how to solve this ? And what does mean an error without error code ?

Thanks !

[Yoruss]

(everything works fine on Android, error only showing up on iOS)