Just curious if both of these developers are trying to use the same ID. I'm not aware of any contention issues but perhaps this is what might be causing the issue. Also, you may need to clear the Power BI cache - sometimes the authentication gets stuck. Clear cache within Power BI (File>options>clear cache)
The only issue I'm aware of is that the "default" tenant for the ID is the only tenant that can be accessed but that sounds unrelated to what you're dealing with.