Thanks for reaching out. We are sorry for the trouble with Lightroom. We are here to help.
Could you please share the specific version to Lightroom from Help > About Lightroom? What operating system are you working on?
Is it a specific album or set of images that do not export?
If your export task includes watermarks, please go to Lightroom > Preferences > Performance > Use Graphics Processor > Set it to Off if it is on Custom or Auto.
If you are on Adobe Lightroom on the desktop (macOS/Windows), try this:
You can create a temporary test album > right-click > Store Album locally > Export from this album.
We hope to hear from you soon,