Description
There’s two issues.
Failed to download or apply critical settings, please check your internet connection. Error info: HTTP 403 (Forbidden)
The URL https://clientsettings.roblox.com/v2/user-channel?binaryType=WindowsPlayer returns a value.
e.g.
{"channelName":"LIVE"}
If this value returns something else that isn’t LIVE the Application seems to set a Registry Value at this path: Computer\HKEY_CURRENT_USER\SOFTWARE\ROBLOX Corporation\Environments\RobloxPlayer\Channel with the type REG_SZ called www.roblox.com to the channel that is returned from the request.
If the channel doesn’t start with the letter z, there will be an issue, which shouldn’t happen just because the name didn’t start with z.
However, when your Registry Values change for the first time by the Roblox Client App, the Application is somehow able to start without any problems. BUT the next time you launch it you’ll receive an Error.
Until you manually erase the Registry Key (which a regular user won’t know how to do).
In the event that a mistake ever occurs on Roblox’s end, this issue would happen.
This could occur from using Third-Party Softwares eventually like “Bloxtrap” 
The second issue is that if a CHANNEL ever gets deleted.
If a channel that starts with the letter z ever gets deleted, literally erased gone. You’ll be soft-locked the same way, with the same problem.
Re-production Steps
This is to re-produce and simulate the issue.
- As a Staff change your own channel to
"help"or something that doesn’t start withz. - Ensure that your channel is currently not
LIVEand set to whatever you’ve set it to by checking this link https://clientsettings.roblox.com/v2/user-channel?binaryType=WindowsPlayer - Start up your Roblox Client App
- You’ll see the Home Screen
- Close Roblox and wait until it closed
- Re-open it
- Observe the error message
Second Issue:
Same thing again, except that you’d be changing it to a channel that does exist and start with the letter z and then you’d delete that channel out of Roblox.
Expected Result
Channels that start with the letter z don’t run into this issue. Any channel name that doesn’t start with a z could run into this issue if the app is launched.
Actual Result
If a channel that doesn’t start with z is returned, the Roblox Client saves this value in the registry and upon the next app launch you’ll get an error.
Failed to download or apply critical settings, please check your internet connection. Error info: HTTP 403 (Forbidden)
Not very informative if the Internet works.