It looks like you’ve seen the posts on how to make it work so it launches into the classic notebook interface? I’ll link again here since others may get here before the older post now. Essentially see my last two posts at the bottom here for the current situation and examples, and links to the related announcement of when JupyterLab became the default interface to open.
Because it is easy to share repository links since things have to be public for the public MyBinder to work, I assume you can provide examples if you are still having issues? I usually can sort out the links needed.