Were you able to stream to Facebook using OBS before upgrading to v27? I started on OBS Studio v25 a year plus ago, and am sticking with v26 for now, and stream weekly to Facebook
Per pinned post in this forum
OBS Studio creates a log file each time you run it which contains very useful diagnostic information. Without a log file, it's much harder for any support volunteers to figure out problems and your post may be ignored. To upload a log file, go to the Help menu > Log Files > Upload Last Log...
obsproject.com
- READ the post about having a recording or streaming session. If streaming isn't working, then record for 30 seconds or more. This info is needed.
If streaming (via OBS) wasn't working before, then there can be LOTS of possible problems. Being free, open source software (FOSS), have you done your part of RTFM? If you are just starting out, I personally recommend looking for a non-gamer oriented tutorial to get started. Once you get streaming working, then, if you are doing so for gaming, look into gaming oriented adjustments/optimizations as a 2nd or later step
Here's the quick-start guide:
OBS Studio - Free and open source software for live streaming and screen recording - obsproject/obs-studio
obsproject.com
Some have recommended the Nerd or Die tutorial video series:
Welcome to our OBS Studio tutorial series! In this series we're going to cover everything that you'll need to know to make your stream look great.Next Video...
www.youtube.com
https://obsproject.com/wiki/
https://obsproject.com/wiki/Dropped-Frames-and-General-Connection-Issues
And when it comes to Facebook, unfortunately for those who aren't tech savvy, and want a pictorial step-by-step, Facebook has been changing /Live/Producer a fair amount since end of last year. So the basics are largely the same (using Camera vs Stream key, Live vs Scheduled Video, etc), but some specific details have varied (especially in created a Scheduled Live Video and the required setup info changed slightly (very minor) just a week or two ago)