“Error 633: The Modem is already in use or not configured properly.”
Solution
Error Causes
This error can be triggered due to several reasons such as:
- A software program conflicts with the USB modem
- The modem is not configured properly
- The Telephon.ini file is missing or damaged
- There is some issue with the way Windows is managing the communication (COM) ports on your computer.
Further Information and Manual Repair
If you experience the Modem Error 633 on your PC, you don’t have to panic. Though this error does not pose any major threats like data loss, it may hamper your ability to use the internet therefore it is advisable to resolve the error. Repairing the Modem Error 633 is quite easy. There are a number of ways to fix this error. So, let’s get started:Solution 1: Delete Incompatible Software and Non-Present Modems
- Click on the start menu and go to the ‘Control Panel’. Now choose the option ‘Phone and Modem’.
- Here you will see three tabs, the dialing rules, modems, and advanced. Choose the tab ‘Modems’. As you click on it, you will see modems installed on your PC. To repair the Modem Error 633, select and remove all the incompatible software and modems that are not present and click ‘OK’.
- Now to bring the changes into effect, restart your system with the modem plugged in and try connecting to the internet again.
Solution 2: Change the Communication Ports
If the error occurs because the modem is not properly configured, then this solution is possibly the best way to resolve this error. Here’s what you need to do:- Click on the Start menu and choose My Computer.
- Now click on the option ‘Manage’ to open the Computer Management Window.
- Once it opens, click the option ‘Device Manager and then expand the option modems. Click on Properties, then the Advanced tab, and the Advanced Port Settings button.
- As you click on the Advanced Port Settings, then click on the COM Port Number drop-down box.
- Choose a new Communication Port. However, make sure it is not already in use.
- Once you make changes, click ‘OK’ and then restart your PC.
- Now Open Device Manager again. Open the Modern Properties Window and then Click the Diagnostics tab.
- After that view the command response window to verify if the error is fixed. If yes, then create a new dial-up connection and connect to the internet with ease.
Solution 3: Disable the Startup items
- Another way to resolve Modem Error 633 on your PC is to go to the start menu and type ‘msconfig’ into the search box and then press ‘enter’.
- Open the misconfig.exe program. As you open it, you will see 4 tabs, General, Boot, Service, Start-up, and Tools.
- Now click on the ‘Start-up’, ‘Disable All’, and then press Apply.
- After you press Apply, a window will pop up asking to restart the computer.
- Confirm it and click restart.
- Once the computer restarts now try connecting to the internet again. This will hopefully resolve the Modem Error 633.

The true cause is that there is no working Border Gateway Protocol (BGP) routes into Facebook's sites. BGP is the standardized exterior gateway protocol used to exchange routing and reachability information between the internet top-level autonomous systems (AS). Most people, indeed most network administrators, never need to deal with BGP.
Cloudflare VP Dane Knecht was the first to report the underlying BGP problem. This meant, as Kevin Beaumont, former Microsoft's Head of Security Operations Centre, tweeted,
"By not having BGP announcements for your DNS name servers, DNS falls apart = nobody can find you on the internet. Same with WhatsApp btw. Facebook has basically de-platformed themselves from their own platform."
Many people are very annoyed by this and with the fact that they cannot use their social media platforms but it seems that Facebook employees are in even bigger annoyance as it was reported that Facebook employees can't enter their buildings because their "smart" badges and doors were also disabled by this network failure. If true, Facebook's people literally can't enter the building to fix things.
Reddit user u/ramenporn, who claimed to be a Facebook employee working on bringing the social network back from the dead, reported, before he deleted his account and his messages:
"DNS for FB services has been affected and this is likely a symptom of the actual issue, and that's that BGP peering with Facebook peering routers has gone down, very likely due to a configuration change that went into effect shortly before the outages happened (started roughly 1540 UTC). There are people now trying to gain access to the peering routers to implement fixes, but the people with physical access is separate from the people with knowledge of how to actually authenticate to the systems and people who know what to actually do, so there is now a logistical challenge with getting all that knowledge unified. Part of this is also due to lower staffing in data centers due to pandemic measures."
Ramenporn also stated that it wasn't an attack, but a mistaken configuration change made via a web interface.
Both BGP and DNS are down, the "connection to the outside world is down, remote access to those tools don't exist anymore, so the emergency procedure is to gain physical access to the peering routers and do all the configuration locally."
Technicians on site don't know how to do that and senior network administrators aren't on site.
It seems that it will all be down for a couple of more hours before the issue is resolved.
Update Windows 11