Even 2years back I was getting this symbol.What does the red symbol indicate?
It clearly means something is wrong/broken.
It may simply mean the connection for the kernel has dropped or timed out. The widget is not communicating properly with something.
However, we cannot provide much guidance because once again your post lacks key details. I have repeatedly asked you to read and follow Getting good answers to your questions and to read and follow the section entitled ’ Help others reproduce the problem’ in the referenced link at the bottom, How do I ask a good question?. That section would explain in bold for emphasis " DO NOT post images of code, data, error messages, etc.." (I’d add that this holds for videos, too.) They are not a good way to share experience. At least not alone. Sometimes they can addd support for a behavior or fleeting action you are trying to describe. The text and shared code in the post alone should provide what is necessary for others to try and help you. That would include details of what you have done to bring you to this point.
An aside is that such a limited figure like this cannot tell us much because other items that would offer clues, such as the kernel status indicator is not shown. So even as support to a clearly written problem with a minimal, reproducible example shared code, this screen grab would be considered lacking.
I think I have also explained before that using a GitHub repo in conjunction with the MyBinder service is one way to both troubleshoot issues and to share examples. I imagine in this case that would be worth pursuing.
Two years back I was supposed to collaborate with the jupyter community for buckaroo and jupyter lab tab extension and this red color symbols where seen when I was working in my jupyter notebook.Again now I connect with jupyter community through Gitbash so this red symbol is seen. My Github is suppose to be the Desktop for jupyter community maybe.